ZWE_1994_DHS_v01_M
Demographic and Health Survey 1994
Name | Country code |
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Zimbabwe | ZWE |
Demographic and Health Survey (standard) - DHS III
The 1994 Zimbabwe Demographic and Health Survey (ZDHS) is the second DHS survey carried out in Zimbabwe. The first one was conducted in 1988.
Sample survey data
The 1994 Zimbabwe Demographic and Health Survey covers the following topics:
The 1994 Zimbabwe Demographic and Health Survey (ZDHS) is a nationally representative survey.
The population covered by the 1994 ZDHS is defined as the universe of all women age 15-49 in Zimbabwe and all men age 15-54 living in the household.
Name |
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Central Statistical Office |
Name | Role |
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Macro International lnc | Technical assitance |
Name | Role |
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U.S. Agency for International Development | Funding |
Name |
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Ministry of Health and Child Welfare |
Zimbabwe National Family |
SAMPLING FRAME
The area sampling frame for the ZDHS was the 1992 Zimbabwe Master Sample (ZMS92), which was developed by the Central Statistical Office (CSO) following the 1992 Population Census for use in demographic and socio-economic surveys. The sample for ZMS92 was designed to be almost nationally representative: people residing on state land (national parks, safari areas, etc.) and in institutions, which account for less than one percent of the total population, were not included. The sample was stratified and selected in two stages. With the exception of Harare and Bulawayo, each of the other eight provinces in the country was stratified into four groups according to land use: communal land, large-scale farming, urban and semi-urban areas, and small scale fanning and resettlement areas. In Harare and Bulawayo, only an urban stratum was formed.
The primary sampling unit (PSU) was the enumeration area (EA), as defined in the 1992 Population Census. A total of 395 EAs were selected with probability proportional to size, the size being the number of households enumerated in the 1992 Population Census. The selection of the EAs was a systematic, one- stage operation, carried out independently for each of 34 strata. In each stratum, implicit stratification was introduced by ordering the EAs geographically within the hierarchy of administrative units (wards and districts within provinces).
An evaluation of the ZMS92 showed that it oversampled urban areas: in the ZMS92 the proportion of urban households is about 36 percent while, according to the preliminary results of the 1992 Population Census, this proportion is about 32 percent.
CHARACTERISTICS OF THE ZDHS SAMPLE
The sample for the ZDHS was selected from the ZMS92 master sample in two stages. In the first stage, 230 EAs were selected with equal probabilities. Since the EAs in the ZMS92 master sample were selected with probability proportional to size from the sampling frame, equal probability selection of a subsample of these EAs for the ZDHS was equivalent to selection with probability proportional to size from the entire sampling frame. A complete listing of the households in the selected EAs was carried out. The list of households obtained was used as the frame for the second-stage sampling, which was the selection of the households to be visited by the ZDHS interviewing teams during the main survey fieldwork. Women between the ages of 15 and 49 were identified in these households and interviewed. In 40 percent of the households selected for the main survey, men between the ages of 15 and 54 were interviewed with a male questionnaire.
SAMPLE ALLOCATION
Stratification in the ZDHS consisted of grouping the ZMS92 strata into two main strata only: urban and rural. Thus the ZDHS rural stratum consists of communal land, large scale farming, and small scale farming and resettlement areas, while the ZDHS urban stratum corresponds exactly to the urban/semi-urban stratum of the ZMS92.
The proportional allocation would result in a completely self-weighting sample but did not allow for reliable estimates for provinces. Results of other demographic and health surveys show that a minimum sample of 1,000 women i:; required in order to obtain estimates of fertility and childhood mortality rates at an acceptable level of sampling errors. Given that the total sample size for the ZDHS could not be increased for the provinces so as to achieve the required level of sampling errors, it was decided that estimates of complex rates would not be produced at the provincial level. Furthermore, since some of the provinces are quite small and would be allocated small sample size, it was decided that the total sample would be allocated equally to the 10 provinces for estimates of selected variables other than complex rates The following sample allocation was adopted after taking into account three factors: (1) a minimum sample of 600 completed interviews for each province; (2) close to proportional allocation for urban and rural areas in each province---except when the resulting stratum size was less than 40, in which case the minimum stratum size was 40--and (3) the number of EAs available in the ZMS92 master sample. According to this sampling scheme, stratum weights would be necessary for data analysis.
A total of 6,483 households were selected, of which 6,075 were found to be occupied. Of the occupied households, 5,984 were successfully interviewed, yielding a household response rate of 98.5 percent. The household response rate shows only moderate variation between provinces. The lowest household response rate was recorded in Harare (95 percent).
Of all eligible women, 95.6 percent were successfully interviewed. Only 0.3 percent of women refused to be interviewed, and 2.4 percent were not at home. A very small percentage (0.2 percent) of interviews with eligible women were incomplete.
Of the eligible men, 91.5 percent were successfully interviewed. The percentage of incomplete inter- views for men is lower than for women because, although only a small percentage (0.6 percent) refused to be interviewed, approximately 4 percent were not at home. The percentage of male interviews completed is higher in rural areas (92.8 percent) than in urban areas (88.9 percent).
Four types of questionnaires were used for the ZDHS: a) the Household Questionnaire, b) the Women's Questionnaire, c) the Men's Questionnaire, and d) the community-level Service Availability Questionnaire. The contents of these questionnaires were based on the DHS Model "A" Questionnaire, which is designed for use in countries with moderate to high levels of contraceptive use.
a) The Household Questionnaire was used to list all the usual members and visitors of selected households. Some basic information was collected on 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 and men who were eligible for the individual interview. In addition, the Household Questionnaire collected information on characteristics of the household's dwelling units, such as the source of water, type of toilel facilities, materials used for the floor of the house, and ownership of various consumer and durable good.
b) The Women's Questionnaire,. was used to collect information on women age 15-49. These women were asked questions on the following topics:
Background characteristics (education, residential history, etc.) Reproductive history Knowledge and use of family planning methods, including compliance with pill use Fertility preference.,:
Unlike the 1988 ZDHS, a "calendar" was used in the 1994 ZDHS to collect information on the respondent' s history since January 1989 concerning reproduction, contraceptive use, reasons for discontinuation of contraception, marriage, anti migration. In addition, interviewing teams measured the height and weight of all children under the age of three years and women who had a birth since January 1991.
c) The Men's Questionnaire was administered to all men age 15-54 living in every 2.5 households in the ZDHS sample (i.e., a 40 percent subsample). The Men's 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.
d) The Service Availability Questionnaire was administered to community leaders during the household listing operations in March 1994. Community-level information was collected on the nearest health and family planning services available to residents of each of the 230 clusters of households included in the ZDHS sample.
Start | End |
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1994-07 | 1994-11 |
Name |
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Central Statistical Office |
Six permanent senior CSO staff coordinated and supervised fieldwork activities.
TRAINING
The ZDHS questionnaires were pretested in April 1994. Twenty qualified nurses were trained to implement the pretest during a three-week training period. Three language versions of the questionnaires were produced: Shona, Ndebele, and English. The pretest fieldwork was conducted over a one-week period in areas surrounding Gweru, where both Shona and Ndebele households could easily be identified. Approxi-mately 150 pretest interviews were conducted, debriefing sessions were subsequently held with the pretest field staff, and modifications to the questionnaire were made based on lessons drawn from the exercise. Pretest interviewers were retained to serve as field editors and team supervisors during the main survey.
Training of field staff for the main survey was conducted over a four-week period, June-July 1994. Permanent CSO staff trained 70 incoming interviewer trainees, most of whom were trained nurses. The training course consisted of instruction in general interviewing techniques, field procedures, a detailed review of items on the questionnaires, instruction and practice in weighing and measuring children, mock interviews between participants in the classroom, and practice interviews with real respondents in areas outside ZDHS sample points. Trainees who performed satisfactorily in the training programme were selected as interviewers, while the remainder were retained to assist in office operations. During this period, field editors and team supervisors were provided with additional training in methods of field editing, data quality control procedures, and coordination of fieldwork.
FIELDWORK
The fleldwork for the ZDHS was carried out by 10 interviewing teams, one designated for each province. Each team consisted of one team supervisor, one field editor, five to six female interviewers, one or two male interviewers and one driver. Thus, in total, there were 10 team supervisors, 10 field editors, 54 female interviewers, 12 male interviewers and 10 drivers. Six permanent senior CSO staff coordinated and supervised fieldwork activities. Data collection took place over a four-month period, 20 July to 28 November 1994.
All questionnaires for the ZDHS were returned to the CSO for data processing, which consisted of office editing, coding of open-ended questions, data entry, and editing computer identified errors. The data were processed on five microcomputers. Data entry and editing were accomplished using the computer program ISSA (Integrated System for Survey Analysis). Data processing commenced on I August 1994 and was completed on 14 December 1994.
Sampling errors, on the other hand, can be evaluated statistically. The sample of respondents 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. 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 ZDHS sample is the result of a two-stage stratified design, and, consequently, it was necessary to use more complex formulae. The computer software used to calculate sampling errors for the ZDHS is the ISSA Sampling Error Module. This module used the Taylor linearisation 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.
In addition to the standard error, ISSA computes the design effect (DEFT) for each estimate, which is defined as the ratio between the s:andard error using the given sample design and the standard error that would result ifa simple random sample had been used. A DEFT value of t .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 samphng 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 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. 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. Sampling errors for selected variables are shown for the 10 provinces. Tables B.2 to B.14 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 DEFY 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.
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 subpopulations. For example, for the variable with secondary education or higher, the relative standard errors as a percent of the e~,;timated mean for the whole country, for urban areas, and for Manicaland are 2.4 percent, 2.9 percent, and 7.4 percent, respectively.
The confidence interval (e.g., as calculated for children ever born ro women age 15-49) can be interpreted as follows: the overall average from the national sample is 2.7 and its standard error is .04. Therefore, to obtain the 95 percent confidence hmits, one adds and subtracts twice the standard error to the sample estimate, i.e., 2.7±.04. There is a high probability (95 percent) that the true average number of children ever born to all women age 15 to 49 is between 2.6 and 2.8.
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 ZDHS to minimise 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 |
Central Statistical Office (CSO) | http://www.zimstat.co.zw/ |
DDI_ZWE_1994_DHS_v01_M
Name | Role |
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World Bank, Development Economics Data Group | Generation of DDI documentation |
2012-03-14
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