The 1992 Zambia Demographic and Health Survey (ZDHS) was a nationally representative sample survey of women age 15-49. The survey was designed to provide information onlevels and trends of fertility, infant and child mortality, family planning knowledge and use, and maternal and child health. The ZDHS was carried out by the University of Zambia in collaboration with Central Statistical Office and the Ministry of Health. Fieldwork was conducted from mid-January to mid-May 1992, during which time, over 6000 households and 7000 women were interviewed.
The primary objectives of the ZDHS are:
- To collect up-to-date information on fertility, infant and child mortality and family planning;
- To collect information on health-related matters such as breastfeeding, antenatal care, children's immunizations and childhood diseases;
- To assess the nutritional status of mothers and children;
- To support dissemination and utilisation of the results in planning, managing and improving family planning and health services in the country; and
- To enhance the survey capabilities of the institutions Involved in order to facilitate the implementation of surveys of this type in the future.
- Results imply that fertility in Zambia has been declining over the past decade or so; at current levels, Zambian women will give birth to an average of 6.5 children during their reproductive years.
- Contraceptive knowledge is nearly universal in Zambia; over 90 percent of married women reported knowing about at least one modern contraceptive method.Over half of women using modern methods obtained them from government sources.
- Women in Zambia am marrying somewhat later than they did previously. The median age at marriage has increased from 17 years or under among women now in their 30s and 40s to 18 years or older among women in their 20s. Women with secondary education marry three years later (19.9) than women with no education (16.7).
- Over one-fifth (22 percent) of currently married women do not want to have any more children.
- One of the most striking findings from the ZDHS is the high level of child mortality and its apparent increase in recent years.
- Information on various aspects of maternal and child healtlr--antenatal care, vaccinations, bmastfeeding and food supplementation, and illness---was collected in the ZDHS on births in the five years preceding the survey.
- ZDHS data indic ate that haft of the births in Zambia are delivered at home and half in health facilities.
- Based on information obtained from health cards and mothers' reports, 95 percent of children age 12- 23 months are vaccinated against tuberculosis, 94 percent have received at least one dose of DPT and polio vaccines, and 77 percent have been vaccinated against measles. Sixty-seven percent of children age 12-23 months have been fully immunised and only 4 percent have not received any immuhisations.
- Almost all children in Zambia (98 percent) are breastfed. The median duration of breasffeeding is relatively long (19 months), but supplemental liquids and foods are introduced at an early age. By age 2-3 months, half of all children are being given supplementary food or liquid.
- ZDHS data indicate that undemutrition is an obstacle to improving child health; 40 percent of children under age five are stunted or short for their age, compared to an international reference population. Five percent of children are wasted or thin for their height and 25 percent are underweight for their age.
- The ZDHS included several questions about knowledge of AIDS. Almost all respondents (99 percent) had heard of AIDS and the vast majority (90 percent) knew that AIDS is transmitted through sexual intercourse.
The implementation of all these aspects of the PHC programmes requires multi-sectoral action and close collaboration among the various govemment institutions. The Govemment has therefore set up multi- sectoral PHC committees as an integral part of the PHC basic supportive manpower and inter-sectoral collaboration with other ministries has been given prominence.
Kind of data
Sample survey data
The 1992 Zambia Demographic and Health Survey (ZDHS) is a nationally representative sample survey, also representative at the level of the nine provinces.
Unit of analysis
- women age 15-49
- Children under five years
All women of reproductive age, age 15-49 in the total sample of households.
Producers and sponsors
University of Zambia
Central Statistical Office
Ministry of Health
Macro International Inc
Agency for International Development
United Nations Population Fund
Norwegian Agency for Development
Government of the Republic of Zambia
United Nations Department of Economic and Social Development
Planned Parenthood Association of Zambia
Technical assitance on questionnaire
National Commission for Development Planning
Technical assitance on questionnaire
Zambia is divided administratively into 9 provinces and 57 districts. In preparation for the 1990 Census of Population, Housing and Agriculture, the entire country was demarcated into Census Supervisory Areas (CSAs). Each CSA was in turn divided into Standard Enumeration Areas (SEAs) of roughly equal size. The measure of size used for selecting the ZDHS sample was the number of households obtained during a quick count operation carried out in 1987. The frame of 4240 CSAs was stratified into urban anti rural areas within each province, with the districts ordered geographically within provinces, thus providing further implicit stratification.
The ZDHS sample was selected from this frame in three stages. First, 262 CSAs (149 in urban areas and 113 in rural areas) were selected from this frame with probability proportional to size (the number of households from the quick count). One SEA was then selected from within each sampled CSA, again with probability proportion to size. The Central Statistical Office (CSO) then organised a household listing operation, in which all structures in the selected SEAs were numbered (on doors), the names of the heads of households were listed and the households were marked by number on sketch maps of the SEAs. These household lists were used to select a systematic sample of households for the third and final stage of sampling. Initially, the objective of the ZDHS sample design was to be able to produce estimates at the national level, for urban and rural areas separately, and for the larger provinces. Since Zambia's population is almost equally divided by urban and rural residence, a self weighting sample was originally designed. Later, it was decided that it would be desirable to be able to produce separate estimates for all nine provinces. To achieve this objective, additional rural CSAs (and SEAs) were selected inLuapula, North- eastern and Western Provinces and the sample take (number of households) in each rural SEA in these provinces was reduced from 42 to 35 in order to minimise the total sample size increase (the sample take was 20 households in urban areas). As a result of this oversampling in Luapula, North-Western and Western Provinces, the ZDHS sample is not self-weighting at the national level.
The results indicate that of the 6709 households selected, ZDHS interviewers successfully interviewed 93 percent. Three percent of the households selected were found to be either vacant or not a valid household, while another 3 percent were absent (not at home). Of the 6458 households that were occupied,96 percent were successfully interviewed (6209). In the interviewed households, 7247 eligible women were found, of whom 97 percent were interviewed (7060).
Dates of collection
Mode of data collection
Two types of questionnaires were used for the ZDHS: (a) the Household Questionnaire and (b) the Individual Questionnaire.
The contents of these questionnaires were based on the DHS Model B Questionnaire, which is designed for use in countries with low levels of contraceptive use. Additions and modifications to the model questionnaires were made after consultation with members of the Department of Social Development Studies of the University of Zambia, the Central Statistical Office (CSO), the Ministry of Health, the Planned Parenthood Association of Zambia (PPAZ), and the National Commission for Development Planning. The questionnaires were developed in English and then translated into and printed in seven of the most widely spoken languages (Bemba, Kaonde, Lozi, Lunda, Luvale, Nyanja and Tonga).
a) The Household Questionnaire was used to list all the usual members and visitors of a selected household. Some basic information was collected on the characteristics of each person listed, including his/her age, sex, education, and relationship to the head of the household. The main purpose of the Household Questionnaire was to identify women who were eligible for the individual interview. In addition, information was collected on the household itself, such as the source of water, type of toilet facilities, material used for the floor of the house, and ownership of various consumer goods.
b) The Individual Questionnaire was used to collect information from women age 15-49 about the following topics: Background characteristics (education, religion, etc.); Reproductive history; Knowledge and use of family planning methods; Antenatal and delivery care; Breastfeeding and weaning practices; Vaccinations and health of children under age five; Marriage; Fertility preferences; Husband's background and respondent's work; and Awareness of AIDS.
In addition, interviewing teams measured the height and weight of all children under age five and their mothers.
Ministry of Health
All questionnaires for the ZDHS were returned to the University of Zambia for data processing. The processing operation consisted of office editing, coding of open-ended questions, data entry, and editing errors found by the computer programs. Two programmers (one from the CSO and one from the University), one questionnaire administrator, two office editors, and three data entry operators were responsible for the data processing operation. The data were processed on four microcomputers owned by the Department of Social Development Studies at the University of Zambia. The ZDHS data entry and editing programs were written in ISSA (Integrated System for Survey Analysis) and followed the standard DHS consistency checks and editing procedures. Simple range and skip errors were corrected at the data entry stage. Secondary machine editing of the data was initiated as soon as a sufficient number of questionnaires had been entered. The purpose of the secondary editing was to detect and correct, if possible, inconsistencies in the data. No major problems were encountered during data editing. Data processing commenced on 22nd January and was completed on 20th June 1992.
Sampling errors, on the other hand, can be evaluated statistically. The sample of women selected in the ZDHS 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 ZDHS sample is the result of a three-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 DEbT 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 ZDHS 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 nine provinces. 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. 13 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 error for most estimates for the country as a whole is 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 rural areas is 1.3 percent, 1.7 percent, and 1.9 percent, respectively.
The confidence interval (e.g., as calculated for EVBORN) can be interpreted as follows: the overall average from the national sample is 3.105 and its standard error is .040. Therefore, to obtain the 95 percent confidence limits, one adds and subtracts twice the standard error to the sample estimate, ie. %105+.080. 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 3.025 and 3.185.
Other forms of data appraisal
Non sampling 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, and data entry errors. Although numerous 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.