The 2013 Yemen National Health and Demographic Survey (2013 YNHDS) is the fourth survey of its kind and follows surveys completed in 1991-1992, 1997, and 2003. The survey is nationwide and calls for a nationally representative sample of about 20,000 households. All women (ever-married and nevermarried) age 15-49 living in the selected households or staying in the households the night before the survey were eligible for individual interview. All women age 15-49 and children between age 6-59 months in onethird of the selected households were eligible for an anemia test. The survey was designed to yield approximately 26,505 completed interviews (18,457 ever-married women and 8,048 never-married women), 7,500 anemia tests of women age 15-49, and about 4,000 anemia tests of children age 659 months. It is designed to provide estimates on the levels of fertility, infant and child mortality, use of contraception and family planning, and family welfare and health indicators.
The 2013 Yemen National Health and Demographic Survey (YNHDS) is the fourth survey of this kind. The primary objective of the survey is to provide up-to-date estimates of basic demographic and health indicators The survey provides information on chronic illness, disability, marriage, fertility and fertility preferences, knowledge and use of family planning methods, child feeding practices, nutritional status of women and children, maternal and childhood mortality, awareness and attitudes regarding HIV/AIDS, female genital cutting, and domestic violence. This information is intended to assist policymakers and program managers in evaluating and designing programs and strategies for improving health and family planning services in the country.
Kind of Data
Sample survey data [ssd]
Unit of Analysis
- Children age 0-5
- Children age 2-14
- Woman age 15-49
The 2013 Yemen National Health and Demographic Survey covered the following topics:
• Household schedule - general information
• Prevalence of chronic diseases and some harmful practices
• Injuries, accidents and health services in the two years preceding the survey
• Controlling children's behavior
• Household characteristics
• Weight, height, hemoglobin measurement for children age 0-5
INDIVIDUAL WOMAN (EVER-MARRIED)
• Background characteristics (age, marital status, education, media exposure, and so on)
• Birth history with information on all living and dead children
• Knowledge and use of family planning methods
• Fertility preferences
• Antenatal, delivery, and postnatal care
• Breastfeeding and infant feeding practices
• Vaccinations and childhood illnesses
• Women’s work and husbands’ background characteristics
• Awareness, attitudes, and behavior regarding AIDS and other sexually transmitted infections (STIs)
• Other health issues
INDIVIDUAL WOMAN (NEVER-MARRIED)
• Background characteristics (age, education, media exposure, and so on)
• Awareness, attitudes, and behavior regarding AIDS
• Other health issues, including prevalence of tumors
• Female genital cutting
• Domestic violence
• Dead woman's background
• Reproduction and contraception
• The health of the deceased before death and the result of last pregnancy
• Causes of death
• Circumstances leading to her death
Producers and sponsors
Ministry of Public Health and Population
Government of Yemen
Central Statistical Organization
Government of Yemen
Pan Arab Program for Family Health
Technical as well as financial assistance
Government of Yemen
Funded the study
United States Agency for International Development
Funded the study
United Nations Population Fund
Funded the study
United Nations Children’s Fund
Funded the study
World Health Organization
Funded the study
The World Bank Group
Funded the study
United Kingdom Department for International Development
Funded the study
Embassy of the Kingdom of the Netherlands
Funded the study
The sample for the 2013 YNHDS was designed to provide population and health indicator estimates at the national and governorate levels. The sample design allowed for specific indicators, such as contraceptive use, to be calculated for each of Yemen’s 20 governorates and Sana’a, the capital city. To have enough cases to report on key indicators in each of the 21 reporting domains, the smallest governorates in terms of population were oversampled while the largest were undersampled. The 2004 General Population Housing and Establishment Census was used as the sampling frame.
During the 2004 census, the country was divided into areas convenient for data collection called census enumeration areas (EAs). The primary sampling unit (PSU), referred to as a cluster for the 2013 YNHDS, is defined on the basis of EAs from the 2004 EA census frame. The 2013 YNHDS sample was selected using a stratified two-stage cluster design consisting of 800 clusters, with 213 in urban areas and 587 in rural areas.
A complete listing of households and a mapping exercise were carried out for each cluster from November 10 to November 30, 2012, with the resulting lists of households serving as the sampling frame for the selection of households in the second stage. All households were listed. In each rural cluster, one household was randomly selected. This household and the next 24 households on the list together constituted the household sample for each of the 587 rural clusters; in urban clusters, the 25 households were randomly selected. The total of 800 clusters was estimated to yield a sample of 20,000 households at the national level. However, for security reasons, ten clusters were not listed.
All ever-married and never-married women age 15-49 in each selected household were eligible to be interviewed. In addition, in one-third of selected households, all women age 15-49 as well as children age 6-59 months were eligible to be tested for anemia.
Note: The sample design is described in detail in Appendix A.
Deviations from the Sample Design
Among the 800 clusters initially selected, ten were not listed and, at the time of data collection, nine additional clusters had not been visited for security reasons. Consequently, the results of the 2013 YNHDS are based on 781 clusters that were actually visited during the data collection phase.
A total of 19,517 households were selected for inclusion in the YNHDS, and of these, 18,027 were occupied. Of the 18,027 occupied households, 17,351 were successfully interviewed, yielding a response rate of 96 percent (97 percent in rural areas compared with 95 percent in urban areas).
In the interviewed households, a total of 17,318 ever-married women were identified to be eligible for the individual interview, and 96 percent of them (16,656) were successfully interviewed. For nevermarried women, 9,488 were identified as eligible for interview, and 93 percent of them (8,778) were successfully interviewed.
Because of the nonproportional allocation of the sample to different governorates and the possible differences in response rates, sampling weight is required for any analysis that uses the 2013 YNHDS data; this ensures the actual representativeness of the survey results at the national level and the domain level. Because the 2013 YNHDS sample is a two-stage stratified cluster sample, sampling weight is calculated based on separate sampling probabilities for each sampling stage and for each cluster.
Design weight is adjusted for household and individual nonresponse to get the sampling weights for household and women surveys, respectively. The differences between the household sampling weight and the individual sampling weights are introduced by individual nonresponse. The final sampling weights are normalized to give the total number of unweighted cases equal to the total number of weighted cases at national level, for both household and individual weights. The normalized weights are relative weights valid for estimating means, proportions, and ratios but not valid for estimating population totals and for pooling data.
Dates of Data Collection
Data Collection Mode
Data Collection Notes
Training of Field Staff
All aspects of data collection were pre-tested from November 20 to December 12, 2012. Twentyfour participants (16 females and 8 males) attended the two-week training in the administration of the YNHDS survey instruments, anthropometric measurement, and hemoglobin testing. Pre-test fieldwork was carried out over four days in urban and rural clusters in and around Sana’a. A total of 124 household interviews (70 in urban and 54 in rural areas) were conducted, in which 161 eligible women were located and interviewed. Following field practice, a debriefing session was held with the pre-test field staff, and modifications to the questionnaires were made based on lessons drawn from the exercise. Unfortunately, the main survey was delayed, and the training for the main survey only took place eight months later.
The four-week main training that took place from August 18 to September 12, 2013, was conducted by MOPHP and CSO staff, and ICF and PAPFAM consultants. In addition, MOPHP nutritionists participated in the biomarker training. The training started with 278 field staff. Due to the very large number of trainees, training was carried out simultaneously in two classrooms. The training included lectures, role playing, mock interviews, and field practices. Several role playing and mock interview sessions were held so that the interviewers got plenty of practice. The training on biomarker collection was held concurrently with the training on questionnaire administration, two one-day field practices took place during the training. The purpose of field practice was to train interviewers on questionnaire delivery as well as height and weight measurement and hemoglobin testing. Overall, the practice sessions were successful, with interviewers generally performing better during the second round. By the end of each field practice, many interviewers had completed two households; in total, all teams completed 228 household questionnaires, 228 ever-married woman questionnaires, 173 never-married woman questionnaires, 445 height and weight measurement sessions, and 400 hemoglobin tests.
Fieldwork was launched simultaneously in all governorates immediately upon the conclusion of field staff training. Forty interviewing teams carried out data collection for the 2013 YNHDS. Each team consisted of one male team supervisor, one male field editor, four female interviewers, and one driver. Fieldwork supervision was conducted by MOPHP, CSO, ICF, PAPFAM, and a technical team through regular visits to teams to review their work and monitor data quality. Data collection took place over a twomonth period, from September 14 through November 23, 2013, with a two-week interruption (October 10-25) due to Adhah Eid. Questionnaires were regularly delivered to MOPHP headquarters.
Four questionnaires were used in the 2013 YNHDS: a household questionnaire, two individual questionnaires (one for ever-married women and an abbreviated version for never-married women), and a maternal mortality questionnaire.
The questionnaires were adapted from model survey instruments developed for the MEASURE DHS project to reflect the population and health issues relevant to Yemen. These issues were identified in consultation with a broad spectrum of government ministries and agencies, nongovernmental organizations, and international donors.
The Household Questionnaire was used to list all the usual members of and visitors to selected households. Basic information was collected on the characteristics of each person listed, including age, sex, marital status, education, and relationship to the head of the household. The Household Questionnaire also collected information on characteristics of the household’s dwelling unit, such as the source of water, type of toilet facilities, materials used for the floor of the dwelling, and ownership of various durable goods. The questionnaire was further used to record height and weight measurements for children age 0-59 months and women age 15-49 years, results of the hemoglobin testing for children age 6-59 months and women age 15-49 years, and results of an iodine test of household cooking salt. The data on the sex, age, and marital status of household members interviewed with the Household Questionnaire were used to identify the women eligible for the ever-married and never-married individual interview.
Several modules or sets of questions were also added to the Household Questionnaire:
• A module on child discipline, developed by UNICEF
• Modules on chronic diseases, disability, and injuries and accidents, developed by PAPFAM
• Questions on food security
An Individual Questionnaire, based on the standard MEASURE DHS Woman’s Questionnaire, was used to collect information from all ever-married women age 15-49.
A simplified version of the ever-married woman’s Individual Questionnaire was used for the nevermarried women.
The 2013 YNHDS did not use the Maternal Mortality module developed by MEASURE DHS (which is based on the sisterhood method). Instead it used a methodology previously used by PAPFAM in the 2003 YFHS. The Maternal Mortality component of the YNHDS was implemented in two phases.
Household listing. The household listing identified 113,463 households in the YNHDS selected clusters. Two types of key information were recorded in each household listed: the number of births and the number of deaths of women age 12-49 over the past two years. All households with a woman's death in the past two years were selected to be interviewed during the main survey. It should be noted that these households were not necessarily the same as those randomly selected for the main survey.
Maternal mortality data collection. During the data collection, all households identified during the listing phase with a woman's death in the past two years (whether or not selected for the main survey) were interviewed using the Maternal Mortality Questionnaire to identify maternal deaths and collect additional information on the deceased women.
The processing of the YNHDS data with the CSPro software began as soon as questionnaires were received from the field. Completed questionnaires were returned from the field to MOPHP headquarters, where they were entered and edited by data processing personnel who were specially trained for this task and who had also attended questionnaire training. Data processing was to be concurrent with data collection to allow for regular monitoring of team performance and data quality. However, data entry was slow during the first few weeks, and the “field check” tables that were supposed to be regularly generated to check various data quality parameters were not produced early enough to provide feedback to the data collection teams during the first weeks of fieldwork. Coding was completed on January 15, 2014, and data entry, which included 100 percent double entry to minimize keying error and data editing, was completed on February 15, 2014. Data cleaning was completed on March 15, 2014. Secondary editing, imputation, and calculation of survey weights were completed by mid-April 2014.
Estimates of Sampling Error
The estimates from a sample survey are affected by two types of errors: nonsampling errors and sampling errors. 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 2013 Yemen HDS (YNHDS) to minimize this type of error, nonsampling 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 2013 YNHDS 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 among 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 respondents had been selected as a simple random sample, it would have been possible to use straightforward formulas for calculating sampling errors. However, the 2013 YNHDS sample is the result of a multi-stage stratified design, and, consequently, it was necessary to use more complex formulas. Sampling errors are computed in either ISSA or SAS, using programs developed by ICF International. These programs use the Taylor linearization method of variance estimation for survey estimates that are means, proportions, or ratios. The Jackknife repeated replication method is used for variance estimation of more complex statistics such as fertility and mortality rates.
The Taylor linearization method 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.
Note: A more detailed description of estimate of sampling error is presented in APPENDIX B of the survey report.
Data Quality Tables
- Household age distribution
- Age distribution of eligible and interviewed women
- Completeness of reporting
- Births by calendar years
- Reporting of age at death in days
- Reporting of age at death in months
- Nutritional status of children based on the NCHS/CDC/WHO International Reference Population
- Need and demand for family planning for currently married women
Note: See detailed data quality tables in APPENDIX C of the report.
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DDI Document ID
Development Data Group
The World Bank
Documentation of the DDI
DDI Document version
Version 01 (July 2015). Metadata is excerpted from "Yemen National Health and Demographic Survey 2013" Report.