The Tanzania Demographic and Health Survey (TDHS) is part of the worldwide Demographic and Health Surveys (DHS) programme, which is designed to collect data on fertility, family planning, and maternal and child health.
The general objectives of the 1996 TDHS are to:
- Provide national-level data that will allow the calculation of demographic rates, particularly fertility and childhood mortality rates
- Analyze the direct and indirect factors which determine the level and trends of fertility
- Measure the level of contraceptive knowledge and practice (of both women and men) by method, by urban-rural residence, and by region
- Collect reliable data on maternal and child health indicators; immunization, prevalence, and treatment of diarrhea and other diseases among children under age five; antenatal visits; assistance at delivery; and breastfeeding
- Assess the nutritional status of children under age five and their mothers by means of anthropometric measurements (weight and height), and child feeding practices
- Assess among women and men the prevailing level of specific knowledge and attitudes regarding AIDS and evaluate patterns of recent behavior regarding condom use
- Measure maternal mortality and collect data on female circumcision.
Kind of data
Sample survey data
The survey was designed to provide estimates (based on the results of the Woman's Questionnaire) for the whole country, for urban and rural areas in the country, and groups of regions (zones). In addition, the sample provides certain estimates for each of the 20 regions in the mainland and 2 subgroups in Zanzibar: Pemba Island and Ungaja.
In most regions, one in every four households was selected for the men's survey, and in six regions (Dares Salaam, Dodoma, Iringa, Kilimanjaro, Morogoro, and Shinyanga), men in every second household were selected for the interview. The sample of men was designed to provide estimates for the country as a whole and for urban and rural areas.
Unit of analysis
- Children under five years
- Women age 15-49
- Men age 15-59
Producers and sponsors
Bureau of Statistics
Macro International Inc.
Ministry of Health
Technical advice and logistical support
United States Agency for Intemational Development
The TDHS sample was a three-stage design consisting of the same 357 enumeration areas (EAs) that were used in the 1991-92 TDHS (262 EAs in rural and 95 EAs in urban areas). The selection of EAs was made in two stages: first, wards/branches and then EAs within wards/branches were selected. Lists of all households were prepared for the selected EAs and, at the third sampling stage; households were selected from these lists. The TDHS was designed to provide estimates (based on the results of the Woman's Questionnaire) for the whole country, for urban and rural areas in the country, and groups of regions (zones). In addition, the sample will provide certain estimates for each of the 20 regions in the mainland and 2 subgroups in Zanzibar: Pemba Island and Ungaja. In most regions, one in every four households was selected for the men's survey, and in six regions (Dares Salaam, Dodoma, Iringa, Kilimanjaro, Morogoro, and Shinyanga), men in every second household were selected for the interview. The sample of men was designed to provide estimates for the country as a whole and for urban and rural areas.
Unlike most other DHS surveys, households in Tanzania were selected from the household listing for each ward (or branch) on the basis of contiguity, beginning with a randomly selected start number. This selection process was used to minimize the difficulty encountered in moving from one selected household to another given the scattered nature of households.
See detailed sample design information in the APPENDIX A of the final 1996 Tanzania Demographic and Health Survey report.
In all, 8,900 households were selected, out of which 8,141 were occupied. Of the households found, 7,969 were interviewed, representing a response rate of 98 percent. The shortfall between the selected and the interviewed households was largely because many dwellings were either vacant or no competent respondents were present at the time of the visit.
In the interviewed households, 8,501 eligible women (i.e. women age 15- 49) were identified for the individual interview, and 8,120 women were actually interviewed, yielding a response rate of 96 percent. In the subsample of households selected for the male interview, 2,658 eligible men (i.e., men age 15-59) were identified, 2,256 were interviewed, representing a response rate of 85 percent. The principal reason for nonresponse among both eligible men and women was the failure to find them at home despite repeated visits to the household. The lower response rates among men than women were due to the more frequent and longer absences of men.
The response rates are lower in urban areas. One-member households are more common in urban areas and are more difficult to interview because they keep their houses locked up most of the time. In urban settings, neighbors often do not know the whereabouts of such people.
Dates of collection
Mode of data collection
Three types of questionnaires were used during the survey. The Household Questionnaire was used to list the names of the household members and certain individual characteristics of all usual members of the household and visitors who had spent the previous night in the household. Certain basic information was collected on characteristics of each person listed, including relationship, age, sex, education, and place of residence. Furthermore, the Household Questionnaire collected information on characteristics relating to the household. These included the source of water, type of toilet facilities, materials used for the floor of the house, and ownership of various durable goods. However, the main purpose of the Household Questionnaire was to identify women and men who were eligible for the individual interview.
The Female Questionnaire was used to collect information from eligible women age 15-49. The topics covered in this questionnaire included the following:
- Background characteristics of the woman including age, education, residential history
- Reproductive history
- Knowledge and use of family planning methods
- Fertility preferences and attitudes about family planning
- Antenatal and delivery care
- Breastfeeding and weaning practices
- Vaccinations and health status of children under age five
- Marriage and sexual activity
- Husband's occupation and education
- Woman's employment, occupation, and earnings
- Awareness and behavior regarding AIDS and other sexually transmitted diseases
- Maternal mortality
- Female circumcision
- Height and weight of children under five years and their mothers.
The Male Questionnaire was used to collect information from a subsample of men age 15-59, namely, those living in every fourth household except in Dares Salaam, Dodoma, Kilimanjaro, Morogoro, Shinyanga, and Iringa regions where every second household was selected for the male interview. The Male Questionnaire collected much of the same information found in the Women's Questionnaire, but was shorter because it did not contain questions on reproductive history and maternal and child health. All questionnaires were translated and printed in Kiswahili.
Before the design of the questionnaires could be finalized, a pretest was done in May-June, 1996 to assess the viability of the questions, the flow and logical sequence of the skip pattern, and the field organization. It covered an area outside Dares Salaam and took about a week to complete. Modifications to the questionnaires were then made based on lessons drawn from the exercise.
The data processing staff for the survey initially consisted of four clerks and one supervisor who were staff of the Bureau of Statistics. However, to speed up the data processing work, an additional four data processing staff were recruited.
All questionnaires for the TDHS were returned to the Bureau of Statistics for data processing, which consisted of office editing, coding of open-ended questions, data entry, and editing of computer-identified errors. All data were processed on microcomputers with a software programme developed for DHS surveys, called the Integrated System for Survey Analysis (ISSA). Data entry was 100 percent verified. Office editing and data processing activities were initiated immediately after the beginning of fieldwork and completed in mid-December, 1996.
The estimates from a sample survey are affected by two types of errors: non-sampling errors, and sampling errors. Non-sampling 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 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 1996 TDHS to minimize this type of error, non-sampling errors are impossible to avoid and difficult to evaluate statistically.
Sampling errors, on the other hand, can be evaluated statistically. The sample of respondents selected in the TDHS 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, straightforward formulae for calculating sampling errors could have been used. However, the TDHS sample is the result of a two-stage stratified design, and, consequently, it was necessary to use more complex formulae. The computer software that calculated sampling errors for the TDHS was the ISSA Sampling Error Module (SAMPERR). 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.
Note: See detailed sampling error calculation in the APPENDIX B of the final 1996 Tanzania Demographic and Health Survey report.
Other forms of data appraisal
Data Quality Tables
- Household age distribution
- Age distribution of eligible and interviewed women
- Completeness of reporting
- Birth by calendar year since birth
- Reporting of age at death in days
- Reporting of age at death in months
- Completeness of information on siblings
- Data on siblings: Indicators on data quality
- Sibship size and sex ratio of siblings
Note: See these data quality tables in APPENDIX C of the 1996 Tanzania Demographic and Health Survey report.
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.
Data and Data Related Resources
World Bank, Development Economics Data Group
Documentation of the study
Version 1.0: (June 2011) Variable level metadata is not provided.