Demographic and Health Survey 1990, Nigeria
Nigeria, 1990
Nigeria. Federal Office of Statistics (FOS)
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Identification
IDNO
nga-fos-dhs-1990-v1
Title
Demographic and Health Survey 1990, Nigeria
Subtitle
Nigeria
Country
| Name | Country code |
|---|---|
| Nigeria | NGA |
Study type
Demographic and Health Survey (standard) - DHS II
Series Information
The 1990 Demographic and Health Survey (NDHS) is the first survey of its kind in Nigeria.
Abstract
The 1990 Nigeria Demographic and Health Survey (NDHS) is a nationally representative survey conducted by the Federal Office of Statistics with the aim of gathering reliable information on fertility, family planning, infant and child mortality, maternal care, vaccination status, breastfeeding, and nutrition. Data collection took place two years after implementation of the National Policy on Population and addresses issues raised by that policy.
Fieldwork for the NDHS was conducted in two phases: from April to July 1990 in the southern states and from July to October 1990 in the northern states. Interviewers collected information on the reproductive histories of 8,781 women age 15-49 years and on the health of their 8,113 children under the age of five years.
OBJECTIVES
The Nigeria Demographic and Health Survey (NDHS) is a national sample survey of women of reproductive age designed to collect data on socioeconomic characteristics, marriage patterns, history of child bearing, breastfeeding, use of contraception, immunisation of children, accessibility to health and family planning services, treatment of children during episodes of illness, and the nutritional status of children.
The primary objectives of the NDHS are:
(i) To collect data for the evaluation of family planning and health programmes;
(ii) To assess the demographic situation in Nigeria; and
(iii) To support dissemination and utilisation of the results in planning and managing family planning and health programmes.
MAIN RESULTS
According to the NDHS, fertility remains high in Nigeria; at current fertility levels, Nigerian women will have an average of 6 children by the end of their reproductive years. The total fertility rate may actually be higher than 6.0, due to underestimation of births. In a 1981/82 survey, the total fertility rate was estimated to be 5.9 children per woman.
One reason for the high level of fertility is that use of contraception is limited. Only 6 percent of married women currently use a contraceptive method (3.5 percent use a modem method, and 2.5 percent use a traditional method). These levels, while low, reflect an increase over the past decade: ten years ago just 1 percent of Nigerian women were using a modem family planning method. Periodic abstinence (rhythm method), the pill, IUD, and injection are the most popular methods among married couples: each is used by about 1 percent of currently married women. Knowledge of contraception remains low, with less than half of all women age 15-49 knowing of any method.
Certain groups of women are far more likely to use contraception than others. For example, urban women are four times more likely to be using a contraceptive method (15 percent) than rural women (4 percent). Women in the Southwest, those with more education, and those with five or more children are also more likely to be using contraception.
Levels of fertility and contraceptive use are not likely to change until there is a drop in desired family size and until the idea of reproductive choice is more widely accepted. At present, the average ideal family size is essentially the same as the total fertility rate: six children per woman. Thus, the vast majority of births are wanted. The desire for childbearing is strong: half of women with five children say that they want to have another child.
Another factor leading to high fertility is the early age at marriage and childbearing in Nigeria. Half of all women are married by age 17 and half have become mothers by age 20. More than a quarter of teenagers (women age 15-19 years) either are pregnant or already have children.
National statistics mask dramatic variations in fertility and family planning between urban and rural areas, among different regions of the country, and by women's educational attainment. Women who are from urban areas or live in the South and those who are better educated want and have fewer children than other women and are more likely to know of and use modem contraception. For example, women in the South are likely to marry and begin childbearing several years later than women in the North. In the North, women continue to follow the traditional pattern and marry early, at a median age of 15, while in the South, women are marrying at a median age of 19 or 20. Teenagers in the North have births at twice the rate of those in the South: 20 births per 1130 women age 15-19 in the North compared to 10 birdas per 100 women in the South. Nearly half of teens in the North have already begun childbearing, versus 14 percent in South. This results in substantially lower total fertility rates in the South: women in the South have, on average, one child less than women in the North (5.5 versus 6.6).
The survey also provides information related to maternal and child health. The data indicate that nearly 1 in 5 children dies before their fifth birthday. Of every 1,000 babies born, 87 die during their first year of life (infant mortality rate). There has been little improvement in infant and child mortality during the past 15 years. Mortality is higher in rural than urban areas and higher in the North than in the South. Undemutrition may be a factor contributing to childhood mortality levels: NDHS data show that 43 percent of the children under five are chronically undemourished. These problems are more severe in rural areas and in the North.
Preventive and curative health services have yet to reach many women and children. Mothers receive no antenatal care for one-third of births and over 60 percent of all babies arc born at home. Only one-third of births are assisted by doctors, trained nurses or midwives. A third of the infants are never vaccinated, and only 30 percent are fully immunised against childhood diseases. When they are ill, most young children go untreated. For example, only about one-third of children with diarrhoea were given oral rehydration therapy.
Women and children living in rural areas and in the North are much less likely than others to benefit from health services. Almost four times as many births in the North are unassisted as in the South, and only one-third as many children complete their polio and DPT vaccinations. Programmes to educate women about the need for antenatal care, immunisation, and proper treatment for sick children should perhaps be aimed at mothers in these areas,
Mothers everywhere need to learn about the proper time to introduce various supplementary foods to breastfeeding babies. Nearly all babies are breastfed, however, almost all breastfeeding infants are given water, formula, or other supplements within the first two months of life, which both jeopardises their nutritional status and increases the risk of infection.
Fieldwork for the NDHS was conducted in two phases: from April to July 1990 in the southern states and from July to October 1990 in the northern states. Interviewers collected information on the reproductive histories of 8,781 women age 15-49 years and on the health of their 8,113 children under the age of five years.
OBJECTIVES
The Nigeria Demographic and Health Survey (NDHS) is a national sample survey of women of reproductive age designed to collect data on socioeconomic characteristics, marriage patterns, history of child bearing, breastfeeding, use of contraception, immunisation of children, accessibility to health and family planning services, treatment of children during episodes of illness, and the nutritional status of children.
The primary objectives of the NDHS are:
(i) To collect data for the evaluation of family planning and health programmes;
(ii) To assess the demographic situation in Nigeria; and
(iii) To support dissemination and utilisation of the results in planning and managing family planning and health programmes.
MAIN RESULTS
According to the NDHS, fertility remains high in Nigeria; at current fertility levels, Nigerian women will have an average of 6 children by the end of their reproductive years. The total fertility rate may actually be higher than 6.0, due to underestimation of births. In a 1981/82 survey, the total fertility rate was estimated to be 5.9 children per woman.
One reason for the high level of fertility is that use of contraception is limited. Only 6 percent of married women currently use a contraceptive method (3.5 percent use a modem method, and 2.5 percent use a traditional method). These levels, while low, reflect an increase over the past decade: ten years ago just 1 percent of Nigerian women were using a modem family planning method. Periodic abstinence (rhythm method), the pill, IUD, and injection are the most popular methods among married couples: each is used by about 1 percent of currently married women. Knowledge of contraception remains low, with less than half of all women age 15-49 knowing of any method.
Certain groups of women are far more likely to use contraception than others. For example, urban women are four times more likely to be using a contraceptive method (15 percent) than rural women (4 percent). Women in the Southwest, those with more education, and those with five or more children are also more likely to be using contraception.
Levels of fertility and contraceptive use are not likely to change until there is a drop in desired family size and until the idea of reproductive choice is more widely accepted. At present, the average ideal family size is essentially the same as the total fertility rate: six children per woman. Thus, the vast majority of births are wanted. The desire for childbearing is strong: half of women with five children say that they want to have another child.
Another factor leading to high fertility is the early age at marriage and childbearing in Nigeria. Half of all women are married by age 17 and half have become mothers by age 20. More than a quarter of teenagers (women age 15-19 years) either are pregnant or already have children.
National statistics mask dramatic variations in fertility and family planning between urban and rural areas, among different regions of the country, and by women's educational attainment. Women who are from urban areas or live in the South and those who are better educated want and have fewer children than other women and are more likely to know of and use modem contraception. For example, women in the South are likely to marry and begin childbearing several years later than women in the North. In the North, women continue to follow the traditional pattern and marry early, at a median age of 15, while in the South, women are marrying at a median age of 19 or 20. Teenagers in the North have births at twice the rate of those in the South: 20 births per 1130 women age 15-19 in the North compared to 10 birdas per 100 women in the South. Nearly half of teens in the North have already begun childbearing, versus 14 percent in South. This results in substantially lower total fertility rates in the South: women in the South have, on average, one child less than women in the North (5.5 versus 6.6).
The survey also provides information related to maternal and child health. The data indicate that nearly 1 in 5 children dies before their fifth birthday. Of every 1,000 babies born, 87 die during their first year of life (infant mortality rate). There has been little improvement in infant and child mortality during the past 15 years. Mortality is higher in rural than urban areas and higher in the North than in the South. Undemutrition may be a factor contributing to childhood mortality levels: NDHS data show that 43 percent of the children under five are chronically undemourished. These problems are more severe in rural areas and in the North.
Preventive and curative health services have yet to reach many women and children. Mothers receive no antenatal care for one-third of births and over 60 percent of all babies arc born at home. Only one-third of births are assisted by doctors, trained nurses or midwives. A third of the infants are never vaccinated, and only 30 percent are fully immunised against childhood diseases. When they are ill, most young children go untreated. For example, only about one-third of children with diarrhoea were given oral rehydration therapy.
Women and children living in rural areas and in the North are much less likely than others to benefit from health services. Almost four times as many births in the North are unassisted as in the South, and only one-third as many children complete their polio and DPT vaccinations. Programmes to educate women about the need for antenatal care, immunisation, and proper treatment for sick children should perhaps be aimed at mothers in these areas,
Mothers everywhere need to learn about the proper time to introduce various supplementary foods to breastfeeding babies. Nearly all babies are breastfed, however, almost all breastfeeding infants are given water, formula, or other supplements within the first two months of life, which both jeopardises their nutritional status and increases the risk of infection.
Kind of Data
Sample survey data
Unit of Analysis
- Household
- Women age 15-49
- Children under five years
- Women age 15-49
- Children under five years
Scope
Notes
The Nigeria Demographic and Health Survey 1990 covers the following topics:
- Anthropometry of children under five
- Background characteristics of the respondent
- Breastfeeding and weaning practices
- Contraception and fertility preferences
- Family planning
- Fertility preferences
- Health, and vaccination status of children
- Husband's background and woman's work
- GPS/Georeferenced-Global Positioning System or Georeferenced Data
- Knowledge and use of contraception
- Marriage
- Reproductive behaviour and intentions
- Reproductive history
- Service Availability
- Anthropometry of children under five
- Background characteristics of the respondent
- Breastfeeding and weaning practices
- Contraception and fertility preferences
- Family planning
- Fertility preferences
- Health, and vaccination status of children
- Husband's background and woman's work
- GPS/Georeferenced-Global Positioning System or Georeferenced Data
- Knowledge and use of contraception
- Marriage
- Reproductive behaviour and intentions
- Reproductive history
- Service Availability
Coverage
Geographic Coverage
The 1990 Nigeria Demographic and Health Survey (NDHS) is a nationally representative survey. The sample was constructed so as to provide national estimates as well as estimates for the four Ministry of Health regions.
Universe
The population covered by the 1990 DHS is defined as the universe of all women age 15-49 in Nigeria.
Producers and sponsors
Primary investigators
| Name |
|---|
| Nigeria. Federal Office of Statistics (FOS) |
Producers
| Name | Role |
|---|---|
| IRD/Macro International Inc. | Technical assistance |
Funding Agency/Sponsor
| Name | Abbreviation | Role |
|---|---|---|
| U.S. Agency for International Development | USAID | Funding |
| Nigerian Government | Funding |
Other Identifications/Acknowledgments
| Name | Role |
|---|---|
| Federal Ministry of Health (FMOH) | Member of Survey Advisory Committee |
| World Health Organisation (WHO) | Member of Survey Advisory Committee |
| Department of Planning Research and Statistics (PRS) | Member of Survey Advisory Committee |
| Department of Primary Health Care (PHC) | Member of Survey Advisory Committee |
| Department of Population Activities (DPA) | Member of Survey Advisory Committee |
| Nigeria Institute for Social and Economic Research (NISER) | Member of Survey Advisory Committee |
| United Nations Children's Fund (UNICEF) | Member of Survey Advisory Committee |
| National population committe (NPC) | Member of Survey Advisory Committee |
| Family Health Services (FHS) | Member of Survey Advisory Committee |
| Planned Parenthood Federation of Nigeria (PPFN) | Member of Survey Advisory Committee |
Sampling
Sampling Procedure
The NDHS Sample was drawn from the National Master Sample for the 1987/1992 National Integrated Survey of Households (NISH) programme being implemented by the Federal Office of Statistics (FOS). NISH, as part of the United Nations National Household Survey Capability Programme, is a multi- subject household-based survey system.
The NISH master sample was created in 1986 on the basis of the 1973 census enumeration areas (EA). Within each state, EAs were stratified into three sectors (urban, semiurban, and rural), from which an initial selection of approximately 8C0 EAs was made from each state. EAs were selected at this stage with equal probability within sectors. A quick count of households was conducted in each of the selected EAs, and a final selection of over 4,000 EAs was made over the entire country, with probability proportional to size. This constitutes the NISH master sample from which the NDHS EAs were subsampled.
Prior to the NDHS selection of EAs, the urban and semiurban sectors of NISH were combined into one category, while the rural retained the NISH classification. A sample of about 10,000 households in 299 EAs was designed with twofold oversampling of the urban stratum, yielding 132 urban EAs and 167 rural EAs. The sample was constructed so as to provide national estimates as well as estimates for the four Ministry of Health regions.
The NDHS conducted its own EA identification and listing operation; a new listing of housing units and households was compiled in each of the selected 299 EAs. For each EA, a list of the names of the head of households was constructed, from which a systematic sample of 34 households was selected to be interviewed. A fixed number of 34 households per EA was taken in order to have better control of the sample size (given the variability in EA size of the NISH sample). Thus, the NDHS sample is a weighted sample, maintaining the twofold over sampling of the urban sector.
The NISH master sample was created in 1986 on the basis of the 1973 census enumeration areas (EA). Within each state, EAs were stratified into three sectors (urban, semiurban, and rural), from which an initial selection of approximately 8C0 EAs was made from each state. EAs were selected at this stage with equal probability within sectors. A quick count of households was conducted in each of the selected EAs, and a final selection of over 4,000 EAs was made over the entire country, with probability proportional to size. This constitutes the NISH master sample from which the NDHS EAs were subsampled.
Prior to the NDHS selection of EAs, the urban and semiurban sectors of NISH were combined into one category, while the rural retained the NISH classification. A sample of about 10,000 households in 299 EAs was designed with twofold oversampling of the urban stratum, yielding 132 urban EAs and 167 rural EAs. The sample was constructed so as to provide national estimates as well as estimates for the four Ministry of Health regions.
The NDHS conducted its own EA identification and listing operation; a new listing of housing units and households was compiled in each of the selected 299 EAs. For each EA, a list of the names of the head of households was constructed, from which a systematic sample of 34 households was selected to be interviewed. A fixed number of 34 households per EA was taken in order to have better control of the sample size (given the variability in EA size of the NISH sample). Thus, the NDHS sample is a weighted sample, maintaining the twofold over sampling of the urban sector.
Response Rate
A total of 9,998 households were selected; of these, 8,999 were successfully interviewed. The shortfall is largely due to households being absent; for which a predominant cause seemed to be for purposes of planting crops. In the interviewed households 9,200 eligible women were identified and 8,781 were successfully interviewed.
Data Collection
Dates of Data Collection
| Start | End |
|---|---|
| 1990-04 | 1990-10 |
Data Collection Mode
Face-to-face
Ethics Approval for Data Collection
Supervisors made sure that all the selected households and eligible respondents for an EA were interviewed, and that assignment sheets for the interviewers and supervisors were duly completed.
Data Collection Notes
PRETEST
A pretest exercise was carried out on NDHS with a view to ensuring that the questions were in a logical sequence, that the translations were comprehensible, appropriate and meaningful, and that the preceded answers were adequate. The pretest was conducted in January and February of 1990. Fieldwork was conducted in both urban and rural EAs and in each of the four regions, and all language questionnaires were tested.
Training lasted two weeks and was comprised of classroom training on the questionnaires and field practice. Invited for the first two days of the training were the FOS regional and state officers from the seven pretest states namely: Anambra, Benue, Boruo, Cross River, Kano, Lagos, and Oyo. Those involved in the intensive training were: six senior officers from FOS headquarters in Lagos, and three female interviewers and one FOS supervisor from each pretest state. In all, 21 newly recruited interviewers and 7 FOS supervisors participated in the pretest training exercise. DHS staffhandled the training on the questionnaire and supervised the field practice. At the end of training, the field staff went back to their respective states for the pretest fieldwork which lasted two weeks. At the end of the fieldwork, the interviewers and supervisors came back to Lagos for a debriefing exercise and all their experiences during the fieldwork were related. The six senior officers and the DHS staff who supervised the data collection in the states also related their experiences. All these experiences were used to improve the quality of the final version of the questionnaire.
RECRUITMENT OF FIELD STAFF
The first activity before the commencement of the main survey data collection was the recruitment of interviewers and supervisors, which took place in March 1990 in the southern states, and in June 1990 in the northern states. The recruitment exercise in each state was done by NDHS project staff in the Lagos headquarters, with the assistance of FOS regional and state officers. Candidates were selected for maturity, minimum educational qualification of West African School Certificate or the General Certificate o f Education (ordinary level), ability to read and speak one of the major Nigerian languages chosen for NDHS, and willingness to work in the field for several months.
In all, 157 female candidates were recruited as interviewers and 30 FOS staff were selected as supervisors, including some who took part in the pretest exercise. At the end of four weeks intensive training, 125 female candidates (100 interviewers and 25 editors) and 25 supervisors were finally selected for the fieldwork. Assessment tests were used in selecting candidates.
TRAINING OF FIELD STAFF
The training of field staff was carried out at four separate centres and in two phases, one in the North and one in the South. The southem training phase took place in Ibadan and Enugu, between March and April 1990. Two teams of two staff persons from FOS and one from DHS conducted the training at the centres. The same trainers conducted the northern phase of the training, which took place at Kaduna and Jos, between June and July 1990. The four FOS staff persons handled both training on the questionnaires and field practice, while DHS staff were available for back-up and technical assistance.
Apart from the interviewers and supervisors who attended the 4-week training sessions, the FOS regional and state officers who served as field coordinators in their respective regions and states were also present at each centre for the first two days of the training. Four data processing officers from FOS headquarters in Lagos attended the training in Ibadan for two weeks, to familiarise themselves with the questionnaire and their responsibilities as data entry personnel for the survey. All training participants were provided accommodations in hotels, and the conference halls in these hotels were the venue for training.
Each training session lasted four weeks. The first two weeks were devoted to classroom lectures, demonstrations of interviewing techniques, and instruction on how to complete the questionnaires and assignment sheets, using the instruction manuals as guides. By the third week of training, interviewers were grouped by language, with their supervisors, for practice reading the questionnaires and role playing.
The fourth week was devoted to practice fieldwork in non-NDHS EAs near the training centre. The interviewers were assigned households to be interviewed in the local language. The completed questionnaires for practice fieldwork were checked by the trainers and supervisors and errors were discussed during the evening sessions before proceeding to the next EA. During training, a series of assessment tests was given to the interviewers and supervisors. These tests were graded and the results were used in selecting interviewers and supervisors; those candidates who had a better grasp of the questionnaire, and were adept at detecting errors in completed questionnaires, were designated as field editors.
Two guest lecturers were invited to each training centre. A staff person from the Planned Parenthood Federation of Nigeria (PPFN) lectured on family planning methods and sources where methods can be obtained, and a staff person from Federal/State Ministry of Health, Primary Health Care Unit lectured on child health and immunisation.
Anthropometry was taught over a two-week period, altemating training time with work on other sections of the individual questionnaire. In the southern phase, training was conducted by a DHS consultant on anthropometry, who was assisted by two FOS staff. In the northern phase, the two FOS staff conducted the anthropometric training. Arrangements were made with nurseries, day care centres, and hospitals for practice measuring of infants and children. All trainees received anthropometric training.
COMPOSITION OF THE FIELDWORK TEAMS
At the end of the one-month training course, the fieldworkers were selected from the larger pool of trainees. Over the four training sites, a total of 100 interviewers and 25 field editors were selected. Fieldwork teams were composed of four female interviewers, one female editor, one male or female supervisor, and one driver. In all, a total of 25 teams were engaged for the main survey. Fifteen teams were used in the southern phase of fieldwork (9 in the Southwest and 6 in the Southeast), and 10 teams were used in the nortbem phase (5 in the Northwest and 5 in the Northeast).
MAIN SURVEY FIELDWORK
The main survey fieldwork commenced immediately after training. The first week of fieldwork was conducted in the states where training took place, covering both urban and rural EAs; one EA per team.
The first week of fieldwork was done in the South in April 1990 and in the North in July 1990. At the end of the first week, a debriefing session was held, during which field staff and trainers related their experiences and problems. There were question and answer sessions and solutions to problems were discussed. The procedures and fieldwork plan and itinerary were discussed before the teams were posted to their respective states for the fieldwork.
Fieldwork for the main survey was conducted in the South between April and July and in the North between July and October 1990.
Thirty-four households were selected for interview in each EA (selection of households was done in the Lagos office from household listings). Women eligible for the individualinterview were identi fled during the household interview. Team supervisors located the housing units and assigned selected households to the interviewers. Completed household and individual questionnaires were handed over to the field editor, who checked to ensure that all relevant questions were correctly recorded, that the skip instructions were properly followed, and that responses were internally consistent. This field editing was done before the team left the EA so that the interviewer could return to the respondent to resolve any errors. Each questionnaire was field edited prior to being sent to the office in Lagos for data entry.
All completed records were then tied together for submission to the FOS state office, for submission to Lagos headquarters.
A pretest exercise was carried out on NDHS with a view to ensuring that the questions were in a logical sequence, that the translations were comprehensible, appropriate and meaningful, and that the preceded answers were adequate. The pretest was conducted in January and February of 1990. Fieldwork was conducted in both urban and rural EAs and in each of the four regions, and all language questionnaires were tested.
Training lasted two weeks and was comprised of classroom training on the questionnaires and field practice. Invited for the first two days of the training were the FOS regional and state officers from the seven pretest states namely: Anambra, Benue, Boruo, Cross River, Kano, Lagos, and Oyo. Those involved in the intensive training were: six senior officers from FOS headquarters in Lagos, and three female interviewers and one FOS supervisor from each pretest state. In all, 21 newly recruited interviewers and 7 FOS supervisors participated in the pretest training exercise. DHS staffhandled the training on the questionnaire and supervised the field practice. At the end of training, the field staff went back to their respective states for the pretest fieldwork which lasted two weeks. At the end of the fieldwork, the interviewers and supervisors came back to Lagos for a debriefing exercise and all their experiences during the fieldwork were related. The six senior officers and the DHS staff who supervised the data collection in the states also related their experiences. All these experiences were used to improve the quality of the final version of the questionnaire.
RECRUITMENT OF FIELD STAFF
The first activity before the commencement of the main survey data collection was the recruitment of interviewers and supervisors, which took place in March 1990 in the southern states, and in June 1990 in the northern states. The recruitment exercise in each state was done by NDHS project staff in the Lagos headquarters, with the assistance of FOS regional and state officers. Candidates were selected for maturity, minimum educational qualification of West African School Certificate or the General Certificate o f Education (ordinary level), ability to read and speak one of the major Nigerian languages chosen for NDHS, and willingness to work in the field for several months.
In all, 157 female candidates were recruited as interviewers and 30 FOS staff were selected as supervisors, including some who took part in the pretest exercise. At the end of four weeks intensive training, 125 female candidates (100 interviewers and 25 editors) and 25 supervisors were finally selected for the fieldwork. Assessment tests were used in selecting candidates.
TRAINING OF FIELD STAFF
The training of field staff was carried out at four separate centres and in two phases, one in the North and one in the South. The southem training phase took place in Ibadan and Enugu, between March and April 1990. Two teams of two staff persons from FOS and one from DHS conducted the training at the centres. The same trainers conducted the northern phase of the training, which took place at Kaduna and Jos, between June and July 1990. The four FOS staff persons handled both training on the questionnaires and field practice, while DHS staff were available for back-up and technical assistance.
Apart from the interviewers and supervisors who attended the 4-week training sessions, the FOS regional and state officers who served as field coordinators in their respective regions and states were also present at each centre for the first two days of the training. Four data processing officers from FOS headquarters in Lagos attended the training in Ibadan for two weeks, to familiarise themselves with the questionnaire and their responsibilities as data entry personnel for the survey. All training participants were provided accommodations in hotels, and the conference halls in these hotels were the venue for training.
Each training session lasted four weeks. The first two weeks were devoted to classroom lectures, demonstrations of interviewing techniques, and instruction on how to complete the questionnaires and assignment sheets, using the instruction manuals as guides. By the third week of training, interviewers were grouped by language, with their supervisors, for practice reading the questionnaires and role playing.
The fourth week was devoted to practice fieldwork in non-NDHS EAs near the training centre. The interviewers were assigned households to be interviewed in the local language. The completed questionnaires for practice fieldwork were checked by the trainers and supervisors and errors were discussed during the evening sessions before proceeding to the next EA. During training, a series of assessment tests was given to the interviewers and supervisors. These tests were graded and the results were used in selecting interviewers and supervisors; those candidates who had a better grasp of the questionnaire, and were adept at detecting errors in completed questionnaires, were designated as field editors.
Two guest lecturers were invited to each training centre. A staff person from the Planned Parenthood Federation of Nigeria (PPFN) lectured on family planning methods and sources where methods can be obtained, and a staff person from Federal/State Ministry of Health, Primary Health Care Unit lectured on child health and immunisation.
Anthropometry was taught over a two-week period, altemating training time with work on other sections of the individual questionnaire. In the southern phase, training was conducted by a DHS consultant on anthropometry, who was assisted by two FOS staff. In the northern phase, the two FOS staff conducted the anthropometric training. Arrangements were made with nurseries, day care centres, and hospitals for practice measuring of infants and children. All trainees received anthropometric training.
COMPOSITION OF THE FIELDWORK TEAMS
At the end of the one-month training course, the fieldworkers were selected from the larger pool of trainees. Over the four training sites, a total of 100 interviewers and 25 field editors were selected. Fieldwork teams were composed of four female interviewers, one female editor, one male or female supervisor, and one driver. In all, a total of 25 teams were engaged for the main survey. Fifteen teams were used in the southern phase of fieldwork (9 in the Southwest and 6 in the Southeast), and 10 teams were used in the nortbem phase (5 in the Northwest and 5 in the Northeast).
MAIN SURVEY FIELDWORK
The main survey fieldwork commenced immediately after training. The first week of fieldwork was conducted in the states where training took place, covering both urban and rural EAs; one EA per team.
The first week of fieldwork was done in the South in April 1990 and in the North in July 1990. At the end of the first week, a debriefing session was held, during which field staff and trainers related their experiences and problems. There were question and answer sessions and solutions to problems were discussed. The procedures and fieldwork plan and itinerary were discussed before the teams were posted to their respective states for the fieldwork.
Fieldwork for the main survey was conducted in the South between April and July and in the North between July and October 1990.
Thirty-four households were selected for interview in each EA (selection of households was done in the Lagos office from household listings). Women eligible for the individualinterview were identi fled during the household interview. Team supervisors located the housing units and assigned selected households to the interviewers. Completed household and individual questionnaires were handed over to the field editor, who checked to ensure that all relevant questions were correctly recorded, that the skip instructions were properly followed, and that responses were internally consistent. This field editing was done before the team left the EA so that the interviewer could return to the respondent to resolve any errors. Each questionnaire was field edited prior to being sent to the office in Lagos for data entry.
All completed records were then tied together for submission to the FOS state office, for submission to Lagos headquarters.
Data Collectors
| Name | Abbreviation |
|---|---|
| Federal Office of Statistics | FOS |
Questionnaires
Questionnaires
The questionnaire for each DHS can be found as an appendix in the final report for each study.
Three questionnaires were used in the main fieldwork for the NDHS: a) the household questionnaire, b) the individual questionnaire, and c) the service availability questionnaire. The first two questionnaires were adapted from the DHS model B questionnaire, which was designed for use in countries with low contraceptive prevalence. The questionnaires were developed in English, and then translated into six of the major Nigerian languages: Efik, Hausa, Igbo, Kanuri, Tiv, and Yoruba.
a) All usual members and visitors in the selected households were listed on the household questionnaire. For each person listed, information was collected on age, sex, education, and relationship to the head of household. The household questionnaire was used to identify women eligible for the individual questionnaire.
b) The individual questionnaire was administered to women age 15-49 who spent the night preceding the household interview in the selected household. Information in the following areas was obtained during the individual interview:
1. Background characteristics of the respondent
2. Reproductive behaviour and intentions
3. Knowledge and use of contraception
4. Breastfeeding, health, and vaccination status of children
5. Marriage
6. Fertility preferences
7. Husband's background and woman's work
8. Height and weight of children under five.
c) The service availability questionnaire was implemented in the service availability survey (SAS), a separate activity from the main fieldwork. The SAS was designed to assess the availability (or supply) of health and family planning services. Thus, while the individual questionnaire collected information from female respondents pertaining to the demand for health and family planning services, the service availability (SA) questionnaire collected information pertaining to the supply of these services by canvassing health and family planning facilities. The SA questionnaire was administered at the community level (enumeration area), and information was gathered from two sources: groups of four or five knowledgeable informants in the selected community (assembled by the interviewer), and informants interviewed at facilities visited by the interviewer.
Three questionnaires were used in the main fieldwork for the NDHS: a) the household questionnaire, b) the individual questionnaire, and c) the service availability questionnaire. The first two questionnaires were adapted from the DHS model B questionnaire, which was designed for use in countries with low contraceptive prevalence. The questionnaires were developed in English, and then translated into six of the major Nigerian languages: Efik, Hausa, Igbo, Kanuri, Tiv, and Yoruba.
a) All usual members and visitors in the selected households were listed on the household questionnaire. For each person listed, information was collected on age, sex, education, and relationship to the head of household. The household questionnaire was used to identify women eligible for the individual questionnaire.
b) The individual questionnaire was administered to women age 15-49 who spent the night preceding the household interview in the selected household. Information in the following areas was obtained during the individual interview:
1. Background characteristics of the respondent
2. Reproductive behaviour and intentions
3. Knowledge and use of contraception
4. Breastfeeding, health, and vaccination status of children
5. Marriage
6. Fertility preferences
7. Husband's background and woman's work
8. Height and weight of children under five.
c) The service availability questionnaire was implemented in the service availability survey (SAS), a separate activity from the main fieldwork. The SAS was designed to assess the availability (or supply) of health and family planning services. Thus, while the individual questionnaire collected information from female respondents pertaining to the demand for health and family planning services, the service availability (SA) questionnaire collected information pertaining to the supply of these services by canvassing health and family planning facilities. The SA questionnaire was administered at the community level (enumeration area), and information was gathered from two sources: groups of four or five knowledgeable informants in the selected community (assembled by the interviewer), and informants interviewed at facilities visited by the interviewer.
Data Processing
Data Editing
Data processing staff for the NDHS consisted of four data entry clerks and one supervisor;, all were FOS staff. They were given periodic assistance by the DHS staff. Four IBM microcomputers were installed in the project office, FOS, Federal Secretariat and were used to process the data. All data entry occurred in the project office in Lagos.
Before questionnaires were passed for data entry, office editing was conducted. This entailed checking for internal consistency of responses recorded in the questionnaire, that skip instructions were properly followed, that there were no omissions, and that all entries were legible. This hastened the work of data entry staff.
Data entry started in April and was completed in October 1990. Once all the data had been entered, a final edit was conducted by running a computer programme to check for inconsistencies, and corrections were made (when possible) by referencing the original questionnaire. This final edit was completed in December 1990. The preliminary report was published in March 1991
Before questionnaires were passed for data entry, office editing was conducted. This entailed checking for internal consistency of responses recorded in the questionnaire, that skip instructions were properly followed, that there were no omissions, and that all entries were legible. This hastened the work of data entry staff.
Data entry started in April and was completed in October 1990. Once all the data had been entered, a final edit was conducted by running a computer programme to check for inconsistencies, and corrections were made (when possible) by referencing the original questionnaire. This final edit was completed in December 1990. The preliminary report was published in March 1991
Data Appraisal
Estimates of Sampling Error
Sampling errors, on the other hand, can be evaluated statistically. The sample of women selected in the NDHS is only one of many samples that could have been selected from the same population, using the same design and expected size. Each of these samples would yield results that differ somewhat from the results of the actual sample selected. The sampling error is a measure of the variability between all possible samples. Although the degree of variability is not known exactly, it can be estimated from the survey results.
Sampling error is usually measured in terms of the standard error for a particular statistic (mean, percentage, etc.), which is the square root of the variance. The standard error can be used to calculate confidence intervals within which the true value for the population can reasonably be assumed to fall. For example, for any given statistic calculated from a sample survey, the value of that statistic will fall within a range of plus or minus two times the standard error of that statistic in 95 percent of all possible samples of identical size and design.
If the sample of women had been selected as a simple random sample, it would have been possible to use straightforward formulas for calculating sampling errors. However, the NDHS sample is the result of a two-stage stratified design, and, consequently, it was necessary to use more complex formulas. The computer package CLUSTERS, developed by the International Statistical Institute for the World Fertility Survey, was used to compute the sampling errors with the proper statistical methodology.
In addition to the standard errors, CLUSTERS computes the design effect (DEFT) for each estimate, which is defined as the ratio between the standard error using the given sample design and the standard error that would result if a simple random sample had been used. A DEFT value of 1.0 indicates that the sample design is as efficient as a simple random sample, while a value greater than 1.0 indicates the increase in the sampling error due to the use of a more complex and less statistically efficient design. CLUSTERS also computes the relative error and confidence limits for the estimates.
Sampling errors for the NDHS are calculated for selected variables considered to be of primary interest. The results are presented in an appendix to the Final Report for the country as a whole, for urban and rural areas, and for the four health zones: Northeast, Northwest, Southeast, and Southwest. For each variable, the type of statistic (mean or proportion) and the base population are given in Table B. 1 of the Final Report. Tables B.2 to B.8 present the value of the statistic (R), its standard error (SE), the number of unweighted (N) and weighted (WN) cases, the design effect (DEFT), the relative standard error (SE/R), and the 95 percent confidence limits (R~SE), for each variable.
In general, the relative standard errors of most estimates for the country as a whole are small, except for estimates of very small proportions. There are some differentials in the relative standard error for the estimates of sub-populations such as geographical areas. For example, for the variable EVBORN (children ever born to women aged 15-49), the relative standard error as a percent of the estimated mean for the whole country, for urban areas and for the Southeast zone is 1.5 percent, 2.3 percent, and 2.7 percent, respectively.
The confidence interval (e.g., as calculated for EVBORN) can be interpreted as follows: the overall average from the national sample is 3.311 and its standard error is .051. Therefore, to obtain the 95 percent confidence limits, one adds and subtracts twice the standard error to the sample estimate, i.e., 3.311+.102. There is a high probability (95 percent) that the true average number of children ever born to all women aged 15 to 49 is between 3.209 and 3.413.
Sampling error is usually measured in terms of the standard error for a particular statistic (mean, percentage, etc.), which is the square root of the variance. The standard error can be used to calculate confidence intervals within which the true value for the population can reasonably be assumed to fall. For example, for any given statistic calculated from a sample survey, the value of that statistic will fall within a range of plus or minus two times the standard error of that statistic in 95 percent of all possible samples of identical size and design.
If the sample of women had been selected as a simple random sample, it would have been possible to use straightforward formulas for calculating sampling errors. However, the NDHS sample is the result of a two-stage stratified design, and, consequently, it was necessary to use more complex formulas. The computer package CLUSTERS, developed by the International Statistical Institute for the World Fertility Survey, was used to compute the sampling errors with the proper statistical methodology.
In addition to the standard errors, CLUSTERS computes the design effect (DEFT) for each estimate, which is defined as the ratio between the standard error using the given sample design and the standard error that would result if a simple random sample had been used. A DEFT value of 1.0 indicates that the sample design is as efficient as a simple random sample, while a value greater than 1.0 indicates the increase in the sampling error due to the use of a more complex and less statistically efficient design. CLUSTERS also computes the relative error and confidence limits for the estimates.
Sampling errors for the NDHS are calculated for selected variables considered to be of primary interest. The results are presented in an appendix to the Final Report for the country as a whole, for urban and rural areas, and for the four health zones: Northeast, Northwest, Southeast, and Southwest. For each variable, the type of statistic (mean or proportion) and the base population are given in Table B. 1 of the Final Report. Tables B.2 to B.8 present the value of the statistic (R), its standard error (SE), the number of unweighted (N) and weighted (WN) cases, the design effect (DEFT), the relative standard error (SE/R), and the 95 percent confidence limits (R~SE), for each variable.
In general, the relative standard errors of most estimates for the country as a whole are small, except for estimates of very small proportions. There are some differentials in the relative standard error for the estimates of sub-populations such as geographical areas. For example, for the variable EVBORN (children ever born to women aged 15-49), the relative standard error as a percent of the estimated mean for the whole country, for urban areas and for the Southeast zone is 1.5 percent, 2.3 percent, and 2.7 percent, respectively.
The confidence interval (e.g., as calculated for EVBORN) can be interpreted as follows: the overall average from the national sample is 3.311 and its standard error is .051. Therefore, to obtain the 95 percent confidence limits, one adds and subtracts twice the standard error to the sample estimate, i.e., 3.311+.102. There is a high probability (95 percent) that the true average number of children ever born to all women aged 15 to 49 is between 3.209 and 3.413.
Data Quality Notes
Nonsampling error is the result of mistakes made in implementing data collection and data processing, such as failure to locate and interview the correct household, misunderstanding of the questions on the part of either the interviewer or the respondent, or data entry errors. Although numerous efforts were made during the implementation of the NDHS to minimize this type of error, nonsampling errors are impossible to avoid and difficult to evaluate statistically.
Access policy
Access authority
| Name | Affiliation | URL | |
|---|---|---|---|
| MEASURE DHS | ICF International | archive@measuredhs.com | www.measuredhs.com |
Contacts
| Name | URL | |
|---|---|---|
| General Inquiries | info@measuredhs.com | www.measuredhs.com |
| Data and Data Related Resources | archive@measuredhs.com | www.measuredhs.com |
| Federal Office of Statistics (FOS) | feedback@nigerianstat.gov.ng | http://www.nigerianstat.gov.ng/ |
Citation requirements
Use of the dataset must be acknowledged using a citation which would include:
- the Identification of the Primary Investigator
- the title of the survey (including country, acronym and year of implementation)
- the survey reference number
- the source and date of download
- the Identification of the Primary Investigator
- the title of the survey (including country, acronym and year of implementation)
- the survey reference number
- the source and date of download
Disclaimer and copyrights
Disclaimer
The user of the data acknowledges that the original collector of the data, the authorized distributor of the data, and the relevant funding agency bear no responsibility for use of the data or for interpretations or inferences based upon such uses.
Metadata production
DDI Document ID
ddi-nga-datafirst-dhs-1990-v1
Producers
| Name | Affiliation | Role |
|---|---|---|
| DataFirst | University of Cape Town | Metadata Producer |
Date of Metadata Production
2012-05-03