The Zimbabwe Demographic and Health Survey (ZDHS) is one of a series of surveys carried out by the Central Statistical Office (CSO) as part of the Zimbabwe National Household Survey Capability Programme. Conducted immediately following the second round of the Intercensal Demographic survey in 1988, the objective of the ZDHS was to make available to policy-makers and planners current information on fertility and child mortality levels and trends, contraceptive knowledge, approval and use and basic indicators of maternal and child health. To obtain these data, a nationally representative sample of 4201 women 15-49 was interviewed in the survey between September 1988 and January 1989.
The ZDHS is one of a series of surveys undertaken by the Central Statistical Office (CSO) as part of the Zimbabwe National Household Survey Capability Programme (ZNHSCP). The ZDHS was conducted immediately after the second round of the Intercensal Demographic Survey (ICDS) in 1988. The main objective of the ZDHS was to provide information on:
- fertility levels, trends and preferences;
- family planning awareness, approval and use;
- maternal and child health, including infant and child mortality;
- and other topics relating to family health.
The survey was designed to obtain information on family planning use similar to that provided by the 1984 Zimbabwe Reproductive Health Survey (ZRHS) and data on fertility and mortality which would complement information collected in the two rounds of the Intercensal Demographic Survey (ICDS). In addition, participation in the worldwide Demographic and Health Survey project offered an opportunity to strengthen survey capability in Zimbabwe, as well as further comparative research by contributing to the international demographic and health database.
Kind of data
Sample survey data
Unit of analysis
- Women age 15-49
- Children under five years
The population covered by the 1988 ZDHS is defined as the universe of all women age 15-49 in Zimbabwe. Eligibility for the individual interview was determined on a de facto basis, i.e., a woman was eligible if she was 15 to 49 years of age and had spent the night prior to the household interview in the household, irrespective of whether she was a usual member of the household or not.
Producers and sponsors
Central Statistical Office
Ministry of Finance, Economic Planning and Development (MFEPD)
Institute for Resource Development/Macro Systems, Inc. (IRD).
Ministry of Health (MOH)
Zimbabwe Family Planning Council (ZNFPC)
U.S. Agency for International Development
the Government of Zimbabwe
Family Health International
Special Funding for awareness of AIDS
To achieve this objective, a nationally representative, self-weighting sample of women 15- 49 was selected and interviewed in the survey. The ZDHS sample was drawn from the Zimbabwe Revised Master Sample (ZRMS). The ZRMS was based on the master sample constructed at the initiation of the Zimbabwe National Household Survey Capability Programme (ZNHSCP) and revised for the first round of the Intercensal Demographic Survey in 1987.
The ZRMS can be considered as a two-stage sample, which is self-weighting at the household level. The sample is stratified by eight provinces and six sectors. The sectors, which are determined by land use include: (1) communal lands, (2) large-scale commercial farming areas, (3) small-scale commercial farming areas, (4) urban and semi-urban areas, (5) resettlement schemes, and (6) national parks, forest and other areas.
A subsample of 167 enumeration areas (EAs) from the 273 EAs in the ZRMS was selected for the ZDHS, including 114 in rural areas and 53 in urban areas. The EAs were selected systematically with probability proportional to the number of households in the 1982 census. Household listings prepared prior to the 1987 ICDS were used in selecting the households to be included in the ZDHS from the selected EAs. All women 15-49 present in the households drawn for the ZDHS sample on the night before the interview were eligible for the survey.
Of the 4789 households selected for the ZDHS, 4337 were located in the field; of these, 4107 households were successfully interviewed. Within the households successfully interviewed, 4467 women were identified as eligible, and, among these eligible women, 4201 women were interviewed. The overall response rate, which is the product of the household (95 percent) and individual (94 percent) response rates was 89 percent.
The overall response rate, which is the product of the household and individual response rate, was 89 percent for the whole sample. It was 90 percent or higher, except in Manicaland (89 percent), Mashonaland East (88 percent) and Harare/Chitungwiza (74 percent).
Dates of collection
Mode of data collection
Two questionnaires were used for the ZDHS, a household and an individual woman's questionnaire. The questionnaires were adapted from the DHS Model "B" Questionnaire, intended for use in countries with low contraceptive prevalence. A pretest was conducted, and the questionnaires were modified, taking into account the pretest results. The household and individual questionnaires were administered in Shona, Ndebele, or English, with these major languages appearing on the same questionnaire.
Information on the age and sex of all usual members and visitors in the selected households was recorded on the household questionnaire and used to identify women eligible for the individual questionnaire. Eligibility for the individual interview was determined on a de facto basis, i.e., a woman was eligible if she was 15 to 49 years of age and had spent the night prior to the household interview in the household, irrespective of whether she was a usual member of the household or not.
The individual questionnaire was used to collect information on the following topics:
- Respondent's background;
- Health and breastfeeding;
- Fertility preferences;
- Husband's background and women's work;
- Height and weight of children 3-60 months.
Data entry and editing began in October 1988 and was completed in February 1989, two weeks after fieldwork ended. The initiation of data processing during the fieldwork allowed the errors that were detected to be communicated immediately to the field teams for corrective measures, thus improving the quality of the data. All data processing activities were carried out in Harare, by a team of five data capture operators under a data processing coordinator. The operators were responsible for office editing and coding, as well as for the entry of the questionnaires. The computer hardware consisted of three IBM-compatible micro-computers. The Integrated System for Survey Analysis (ISSA) software package, developed by IRD for the DHS programme, was used for all phases of the data entry, editing and tabulation. Range, skip and most consistency checks were performed during the data capture itself; only the more sophisticated consistency checks were done during secondary editing.
Sampling error is a measure of the variability between all possible samples that could have been selected from the same population using the same design and size. For the entire population and for large subgroups, the ZDHS sample is sufficiently large so that the sampling error for most estimates is small. However, for small subgroups, sampling errors are larger and, thus, affect the reliability of the data.
Sampling error is usually measured in terms of the standard error for a particular statistic (mean, percentage, ratio, etc.), i.e., the square root of the variance. The standard error can be used also 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 as measured in 95 percent of all possible samples with the same design will fall within a range of plus or minus two times the standard error for that statistic.
The computations required to provide sampling errors for survey estimates which are based on complex sample designs like those used for the ZDHS survey are more complicated than those based on simple random samples. The software package CLUSTERS was used to assist in computing the sampling errors with the proper statistical methodology. The CLUSTERS program treats any percentage or average as a ratio estimate, r=y/x, where y represents the total sample value for variable y and x represents the total number of cases in the group or subgroup under consideration.
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 estimates.
Sampling errors are presented below for selected variables considered to be of major interest. Results are presented in the Final Report for the whole country, urban and rural areas, three broad age groups and three educationaI levels. For each variable, the type of statistic (mean, proportion) and the base population are given in B.1 of the Final Report. For each variable, Tables B.2-B.5 present the value of the statistic, its standard error, the number of unweighted and weighted cases, the design effect, the relative standard errors, and the 95 percent confidence limits.
The relative standard error for most estimates for the country as a whole is small, which means that the ZDHS results are reliable. There are some differentials in the relative standard error for the estimates by region and age groups. For example, for the variable, the proportion ever using a contraceptive method, the relative standard error as a percent of the estimated proportion for the whole country, for urban areas and for rural areas is 1,2 percent, 1,8 percent and 1,5 percent, respectively.
The confidence interval has the following interpretation. The mean number of children ever born among all women is 2,953 and its standard error is 0,045. Therefore, to obtain the upper bound of the 95 percent confidence limit, twice the standard error, i.e., 0,09, is added to the sample mean. To obtain the lower bound, the same amount is subtracted from the mean. There is a high probability (95 percent) that the true mean ideal number of children falls within the interval of 2,862 and 3,044.
Other forms of data appraisal
Non-sampling error is the result of mistakes made in carrying out data collection and data processing, including the failure to locate and interview the correct household, errors in the way questions are asked, and data entry errors. Although efforts were made during the implementation of the ZDHS to minimize this type of error, non-sampling errors are impossible to avoid and difficult to evaluate statistically.
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
Disclaimer and copyrights
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.