Demographic and Health Survey 1988 - Zimbabwe

Abstract
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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.

Geographic coverage
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National

Analysis unit
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- Household
- Women age 15-49
- Children under five years

Universe
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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.

Kind of data
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Sample survey data

Sampling procedure
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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.

Mode of data collection
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Face-to-face

Research instrument
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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;
- Reproduction;
- Contraception;
- Health and breastfeeding;
- Marriage;
- Fertility preferences;
- Husband's background and women's work;
- Height and weight of children 3-60 months.

Cleaning operations
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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.

Response rate
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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).

Sampling error estimates
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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.

Data appraisal
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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.

摘要
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津巴布韦人口与健康调查（ZDHS）是津巴布韦国家统计局（CSO）在津巴布韦国家家庭调查能力计划（ZNHSCP）框架下实施的一系列调查之一。该调查紧随1988年进行的间年人口普查调查的第二轮之后展开，其目标是为政策制定者和规划者提供有关生育和儿童死亡率水平及趋势、避孕知识、接受度和使用情况以及母婴健康基本指标的最新信息。为了获取这些数据，1988年9月至1989年1月期间，对4201名15至49岁的女性进行了全国代表性样本的访谈。

ZDHS是津巴布韦国家统计局（CSO）在津巴布韦国家家庭调查能力计划（ZNHSCP）框架下开展的一系列调查之一。ZDHS是在1988年进行的间年人口普查调查（ICDS）第二轮之后立即进行的。ZDHS的主要目标是提供以下方面的信息：
- 生育水平、趋势和偏好；
- 家庭规划意识、接受度和使用情况；
- 母婴健康，包括婴儿和儿童死亡率；
- 以及与家庭健康相关的其他话题。

调查旨在获取与1984年津巴布韦生殖健康调查（ZRHS）类似的家庭规划使用信息，以及补充间年人口普查调查（ICDS）两轮收集的信息的生育和死亡率数据。此外，参与全球人口与健康调查项目为加强津巴布韦的调查能力以及通过为国际人口与健康数据库做出贡献，进一步开展比较研究提供了机会。

地理覆盖范围
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全国

分析单元
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- 家庭
- 15-49岁女性
- 5岁以下儿童

总体
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1988年ZDHS涵盖的总体是津巴布韦所有15-49岁女性的总体。个人访谈的资格以实际存在为基础，即，如果一位女性在家庭访谈前一夜在家庭中过夜，且年龄在15至49岁之间，则她有资格参与访谈，无论她是否是家庭的常住成员。

数据类型
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样本调查数据

抽样程序
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为了实现这一目标，选择了全国代表性的、自加权女性15-49岁样本进行调查。ZDHS样本是从津巴布韦修订的主样本（ZRMS）中抽取的。ZRMS基于津巴布韦国家家庭调查能力计划（ZNHSCP）启动时构建的主样本，并在1987年第一轮间年人口普查调查中进行了修订。

ZRMS可以被视为一个两阶段样本，在家庭层面上是自加权的。样本按八个省份和六个部门进行分层。这些部门由土地利用决定，包括：（1）集体土地，（2）大规模商业耕作区，（3）小规模商业耕作区，（4）城市和准城市地区，（5）定居点，（6）国家公园、森林和其他地区。

从ZRMS的273个普查区中选取了167个普查区用于ZDHS，包括114个农村地区和53个城市地区。普查区是按照1982年人口普查中家庭数量的比例系统选取的。1987年ICDS之前准备的 household listings 用于从选定的普查区中选择纳入ZDHS的household。在访谈前夜被抽中的ZDHS样本家庭中的所有15-49岁女性都有资格参与调查。

数据收集方式
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面对面

研究工具
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ZDHS使用了两个问卷，一个是家庭问卷，另一个是个人女性问卷。问卷改编自DHS“B”型问卷，旨在用于避孕率较低的国家。进行了预测试，并根据预测试结果对问卷进行了修改。家庭和个人问卷以绍纳语、恩德贝莱语或英语进行，这三种主要语言都出现在同一份问卷上。

家庭问卷上记录了所有常住成员和访客的年龄和性别信息，并用于确定有资格接受个人问卷的女性。个人访谈的资格以实际存在为基础，即，如果一位女性在家庭访谈前一夜在家庭中过夜，且年龄在15至49岁之间，则她有资格参与访谈，无论她是否是家庭的常住成员。

个人问卷用于收集以下主题的信息：
- 受访者的背景；
- 再生产；
- 避孕；
- 健康和母乳喂养；
- 婚姻；
- 生育偏好；
- 丈夫的背景和女性的工作；
- 3-60个月儿童的身高和体重。

数据清洗操作
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数据录入和编辑始于1988年10月，并于1989年2月完成，即现场工作结束后的两周。在实地工作中启动数据处理工作，使得检测到的错误能够立即传达给现场团队进行纠正措施，从而提高了数据质量。所有数据处理活动均在哈拉雷进行，由一名数据处理协调员和五名数据捕获操作员组成的小组完成。操作员负责办公室编辑和编码，以及问卷的录入。计算机硬件包括三台IBM兼容型微型计算机。用于所有数据录入、编辑和制表的Integrated System for Survey Analysis（ISSA）软件包由IRD为DHS项目开发。

响应率
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在为ZDHS选定的4789个家庭中，4337个在实地中被定位；其中，4107个家庭成功接受了访谈。在成功接受访谈的家庭中，确定了4467名有资格的女性，在这些有资格的女性中，4201名女性接受了访谈。总体响应率，即家庭（95%）和个人（94%）响应率的乘积为89%。

总体响应率，即家庭和个人响应率的乘积，对于整个样本为89%。除了马尼卡兰（89%）、马绍纳兰东（88%）和哈拉雷/奇通瓦（74%）之外，都为90%或更高。

抽样误差估计
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抽样误差是衡量在相同的方案和规模下，从同一总体中选取的所有可能样本之间差异的指标。对于整个总体和大型子群体，ZDHS样本足够大，因此大多数估计的抽样误差都很小。然而，对于小型子群体，抽样误差较大，因此会影响数据的可靠性。

抽样误差通常以特定统计量（平均值、百分比、比率等）的标准误差来衡量，即方差的平方根。标准误差也可用于计算置信区间，其中可以合理地假设总体真实值的范围。

为基于复杂样本设计（如ZDHS调查所使用的）的抽样估计提供抽样误差的计算比基于简单随机样本的计算更复杂。用于帮助计算抽样误差的正确统计方法的软件包CLUSTERS被用于此。

除了标准误差之外，CLUSTERS还为每个估计计算设计效应（DEFT），定义为使用给定样本设计计算的标准误差与如果使用简单随机样本将产生的标准误差之间的比率。DEFT值为1.0表示样本设计与简单随机样本一样有效，而大于1.0的值表示由于使用更复杂且统计效率较低的方案而增加的抽样误差。

CLUSTERS还计算估计的相对误差和置信限。

下表展示了被认为具有重大意义的选定变量的抽样误差。结果在最终报告中以整个国家、城市和农村地区、三个广泛年龄组和三个教育水平进行展示。对于每个变量，统计量类型（平均值、比例）和基数人口在最终报告的B.1部分给出。对于每个变量，B.2-B.5表展示了统计量的值、其标准误差、未加权案例和加权案例的数量、设计效应、相对标准误差和95%置信限。

对于整个国家的估计，大多数估计的相对标准误差都很小，这意味着ZDHS的结果是可靠的。对于按地区和年龄组进行的估计，相对标准误差存在一些差异。例如，对于变量“曾经使用过避孕方法的比率”，相对于整个国家估计的比率的相对标准误差、城市地区的相对标准误差和农村地区的相对标准误差分别为1.2%、1.8%和1.5%。

置信区间的解释如下。所有女性中曾经出生的孩子的平均数为2,953，其标准误差为0.045。因此，为了获得95%置信区间的上限，将两倍的标准误差，即0.09，加到样本均值上。为了获得下限，从均值中减去相同的金额。有很高的概率（95%）认为真正的理想平均孩子数为2,862至3,044之间。

数据评估
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非抽样误差是由于在执行数据收集和数据处理过程中出现的错误造成的，包括未能找到和访谈正确的家庭、提问方式错误和数据录入错误。尽管在ZDHS的实施过程中努力最大限度地减少此类错误，但非抽样误差是不可避免的，并且难以从统计上进行评估。