NGA_2003_DHS_v01_M
Demographic and Health Survey 2003
Name | Country code |
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Nigeria | NGA |
Demographic and Health Survey (standard) - DHS IV
The 2003 Demographic and Health Survey (NDHS) is the third survey of its kind in Nigeria.
Sample survey data
The Nigeria Demographic and Health Survey 2003 covers the following topics:
National
The population covered by the 2003 DHS is defined as the universe of all women age 10-49 who were either permanent residents of the households in the 2003 NDHS sample or visitors present in the household on the night before the survey were eligible to be interviewed. In addition, in a subsample of one-third of all households selected for the survey, all men age 15-59 were eligible to be interviewed if they were either permanent residents or visitors present in the household on the night before the survey.
Name |
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National Population Commission |
Name | Role |
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ORC/Macro | Technical assistance |
Name | Role |
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U.S. Agency for International Development | Funding |
Name | Role |
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Department for International Development (DFID) | Support for the survey |
United Nations Population Fund (UNFPA) | Support for the survey |
United Nations Children’s Fund (UNICEF) | Support for the survey |
The principal objective of the 2003 NDHS is to provide current and reliable data on fertility and family planning behaviour, child mortality, children's nutritional status, the utilization of maternal and child health services, and knowledge and attitudes towards HIV/AIDS. A related objective is to provide as many of these key indicators as possible for urban and rural areas separately, as well as for each of Nigeria's six geopolitical zones.
The population covered by the 2003 NDHS is defined as the universe of all women age 15-49 and all men age 15-59 in Nigeria. A probability sample of households was selected and all women age 15-49 identified in the households were eligible to be interviewed. In addition, in a subsample of one-third of the households selected for the survey, all men age 15-59 were eligible to be interviewed.
SAMPLE FRAME
The sample frame for this survey was the list of enumeration areas (EAs) developed for the 1991 Population Census. Administratively, at the time the survey was planned, Nigeria was divided into 36 states and the Federal Capital Territory (FCT) of Abuja. Each state was subdivided into local government area (LGA) units and each LGA was divided into localities. In addition to these administrative units, for implementation of the 1991 Population Census, each locality was subdivided into enumeration areas (EAs). The list of approximately 212,080 EAs, with household and population information (from the 1991census) for each EA, was evaluated as a potential sampling frame for the 2003 NDHS. The EAs are grouped by states, by LGAs within a state, and by localities within an LGA, stratified separately by urban and rural areas. Any locality with less than 20,000 population constitutes a rural area. Also available from the 1991 census were maps showing the location of the EAs. These maps needed to be updated in the field before the final household selection. After a careful evaluation, the EA list was used as the sample frame.
SAMPLE ALLOCATION
The primary sampling unit (PSU), or cluster, for the 2003 NDHS is defined as one or more EAs from the 1991 census frame. A minimum requirement of 50 households per cluster was imposed on the design; in the case of less than 50 households, a contiguous EA was added. The number of clusters in each state was not allocated in proportion to the state's population because of the need to obtain estimates for each of the six zones. Since Nigeria is a country where the majority of the population resides in rural areas, the number of clusters allocated to the urban areas in five out of the six zones was increased in order to obtain reasonable urban estimates.
The target of the 2003 NDHS sample was to obtain completed interviews with about 8,250 women. Based on the level of nonresponse found in the 1999 Nigeria DHS survey, a target of 7,935 households was set. When the sample was implemented, three clusters could not be visited because of communal clashes, so 7,864 households were selected, in which all women age 15-49 were eligible to be interviewed. To obtain estimates of fertility and child mortality with a reasonable level of precision, a minimum of 1,200 completed interviews with women was desired in each zone. In each state, the number of households was not distributed proportionally between urban and rural areas. Also, in six designated states, a minimum of 350 completed interviews were targeted to provide selected indicators.
SAMPLE SELECTION
The 2003 NDHS sample was selected using a stratified, two-stage cluster design. A total of 365 clusters were selected, 165 in urban and 200 in rural areas. Once the number of households was allocated to each state by urban and rural areas, the numbers of clusters was calculated based on an average sample take of 20 completed women's interviews (in 19 selected households) in urban areas, and 25 completed interviews (in 24 selected households) in rural areas. In each urban or rural area in a given state, clusters were selected systematically with equal probability.
SAMPLE FOR MALE SURVEY
In every third household selected, all men age 15-59 listed in the household were eligible to be interviewed. Based on data from the 1999 NDHS, this was expected to produce a total of about 2,800 successfully completed male interviews in the 2003 NDHS.
Table shows household and individual response rates for the 2003 NDHS. A total of 7,864 households were selected for the sample, of which 7,327 were found. The shortfall is largely due to structures that were found to be vacant. Of the 7,327 existing households, 7,225 were successfully interviewed, yielding a household response rate of 99 percent. In these households, 7,985 women were identified as eligible for the individual interview.
Interviews were completed with 95 percent of them. Of the 2,572 eligible men identified, 91 percent were successfully interviewed. There is little difference between urban and rural response rates.
Three questionnaires were used for the 2003 NDHS: the Household Questionnaire, the Women's Questionnaire, and the Men's Questionnaire. The content of these questionnaires was based on the model questionnaires developed by the MEASURE DHS+ programme for use in countries with low levels of contraceptive use. The questionnaires were adapted during a technical workshop organized by the National Population Commission to reflect relevant issues in population and health in Nigeria. The workshop was attended by experts from the government, NGOs, and international donors. The adapted questionnaires were translated from English into the three major languages (Hausa, Igbo, and Yoruba) and pretested during November 2002.
a) The Household Questionnaire was used to list all usual members and visitors in the selected households. Some basic information was collected on the characteristics of each person listed, including age, sex, education, and relationship to the head of the household. The main purpose of the Household Questionnaire was to identify women and men who were eligible for the individual interview. The Household Questionnaire also collected information on characteristics of the household's dwelling unit, such as the source of water, type of toilet facilities, materials used for the floor of the house, ownership of various durable goods, and ownership and use of mosquito nets. Additionally, the Household Questionnaire was used to record height and weight measurements of women age 15-49 and children under the age of 6.
b) The Women's Questionnaire was used to collect information from all women age 15-49. These women were asked questions on the following topics:
c) The Men's Questionnaire was administered to all men age 15-59 living in every third household in the 2003 NDHS sample. The Men's Questionnaire collected much of the same information found in the Women's Questionnaire, but was shorter because it did not contain a reproductive history or questions on maternal and child health or nutrition.
Start | End |
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2003-03 | 2003-08 |
Name |
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National Population Commission |
In addition, quality control personnel independently reinterviewed selected households after the departure of the teams. These checks were performed periodically through the duration of the fieldwork. ORC Macro also participated in field supervision.
TRAINING OF FIELD STAFF
Over 100 people were recruited by the NPC to serve as supervisors, field editors, male and female interviewers, quality control personnel, and reserve interviewers. Efforts were made to recruit high-calibre personnel who came from all of the 36 states and the FCT to ensure appropriate linguistic and cultural diversity. They all participated in the main interviewer training, which was conducted from February 17 to March 8, 2003. The training was conducted in English and included lectures, presentations by outside experts, practical demonstrations, and practice interviewing in small groups. The practice interviews were conducted in the languages that the questionnaires were translated into: English, Hausa, Igbo, and Yoruba. Practice in certain less common dialects was also accomplished by translating directly from the English questionnaires. All of the field staff participated in three days of field practice. Finally, a series of special lectures was held specifically for the group comprising supervisors, field editors, quality control personnel, and field coordinators.
FIELDWORK
Fieldwork for the 2003 NDHS took place over a five-month period, from March to August 2003. Twelve interviewing teams carried out data collection. Each team consisted of one team supervisor, one field editor, four female interviewers, one male interviewer, and one driver. Special care was taken to monitor the quality of data collection. First, the field editor was responsible for reviewing all questionnaires for quality and consistency before the team's departure from the cluster. The field editor and supervisor would also sit in on interviews periodically. Twelve staff assigned from the NPC coordinated fieldwork activities and visited the teams at regular intervals to monitor the work.
The processing of the 2003 NDHS results began shortly after the fieldwork commenced. Completed questionnaires were returned periodically from the field to NPC headquarters in Abuja, where they were entered and edited by data processing personnel who were specially trained for this task. The data processing personnel included two supervisors, a questionnaire administrator (who ensured that the expected numbers of questionnaires from all clusters were received), three office editors, 12 data entry operators, and a secondary editor. The concurrent processing of the data was an advantage since the NPC was able to advise field teams of problems detected during the data entry. In particular, tables were generated to check various data quality parameters. As a result, specific feedback was given to the teams to improve performance. The data entry and editing phase of the survey was completed in September 2003.
Sampling errors, on the other hand, can be evaluated statistically. The sample of respondents selected in the 2003 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. Sampling errors are 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.
A 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 respondents had been selected as a simple random sample, it would have been possible to use straightforward formulas for calculating sampling errors. However, the 2003 NDHS sample is the result of a multi-stage stratified design, and, consequently, it was necessary to use more complex formulae. The computer software used to calculate sampling errors for the 2003 NDHS is the ISSA Sampling Error Module. This module used the Taylor linearization method of variance estimation for survey estimates that are means or proportions. The Jackknife repeated replication method is used for variance estimation of more complex statistics such as fertility and mortality rates.
The Jackknife repeated replication method derives estimates of complex rates from each of several replications of the parent sample, and calculates standard errors for these estimates using simple formulae. Each replication considers all but one clusters in the calculation of the estimates. Pseudo-independent replications are thus created. In the 2003 NDHS, there were 362 non-empty clusters. Hence, 361 replications were created.
In addition to the standard error, ISSA 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. ISSA also computes the relative error and confidence limits for the estimates.
Sampling errors for the 2003 NDHS are calculated for selected variables considered to be of primary interest for woman's survey and for man's surveys, respectively. The results are presented in an appendix to the Final Report for the country as a whole, for urban and rural areas, and for each of the 6 regions. For each variable, the type of statistic (mean, proportion, or rate) and the base population are given in Table B.1 of the Final Report. Tables B.2 to B.10 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±2SE), for each variable. The DEFT is considered undefined when the standard error considering simple random sample is zero (when the estimate is close to 0 or 1). In the case of the total fertility rate, the number of unweighted cases is not relevant, as there is no known unweighted value for woman-years of exposure to childbearing.
The confidence interval (e.g., as calculated for children ever born to women aged 40-49) can be interpreted as follows: the overall average from the national sample is 6.808 and its standard error is 0.134. Therefore, to obtain the 95 percent confidence limits, one adds and subtracts twice the standard error to the sample estimate, i.e., 6.808±2×0.134. There is a high probability (95 percent) that the true average number of children ever born to all women aged 40 to 49 is between 6.540 and 7.077.
Sampling errors are analyzed for the national woman sample and for two separate groups of estimates: (1) means and proportions, and (2) complex demographic rates. The relative standard errors (SE/R) for the means and proportions range between 1.1 percent and 32.7 percent with an average of 6.36 percent; the highest relative standard errors are for estimates of very low values (e.g., currently using female sterilization). If estimates of very low values (less than 10 percent) were removed, then the average drops to 4.2 percent. So in general, the relative standard error for most estimates for the country as a whole is small, except for estimates of very small proportions. The relative standard error for the total fertility rate is small, 2.5 percent. However, for the mortality rates, the average relative standard error is much higher, 6.04 percent.
There are differentials in the relative standard error for the estimates of sub-populations. For example, for the variable want no more children, the relative standard errors as a percent of the estimated mean for the whole country, and for the urban areas are 4.9 percent and 6.1 percent, respectively.
For the total sample, the value of the design effect (DEFT), averaged over all variables, is 1.78 which means that, due to multi-stage clustering of the sample, the average standard error is increased by a factor of 1.78 over that in an equivalent simple random sample.
Nonsampling errors are the results 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, and data entry errors. Although numerous efforts were made during the implementation of the 2003 Nigeria Demographic and Health Survey (NDHS) to minimize this type of error, nonsampling errors are impossible to avoid and difficult to evaluate statistically.
Name | Affiliation | URL | |
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MEASURE DHS | ICF International | www.measuredhs.com | archive@measuredhs.com |
Use of the dataset must be acknowledged using a citation which would include:
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.
Name | URL | |
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General Inquiries | info@measuredhs.com | www.measuredhs.com |
Data and Data Related Resources | archive@measuredhs.com | www.measuredhs.com |
DDI_NGA_2003_DHS_v01_M
Name | Role |
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World Bank, Development Economics Data Group | Generation of DDI documentation |
2012-05-03
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