The 1992-93 National Family Health Survey (NFHS) is the first survey of its kind in India.
The National Family Health Survey (NFHS) was carried out as the principal activity of a collaborative project to strengthen the research capabilities of the Population Reasearch Centres (PRCs) in India, initiated by the Ministry of Health and Family Welfare (MOHFW), Government of India, and coordinated by the International Institute for Population Sciences (IIPS), Bombay. Interviews were conducted with a nationally representative sample of 89,777 ever-married women in the age group 13-49, from 24 states and the National Capital Territoty of Delhi. The main objective of the survey was to collect reliable and up-to-date information on fertility, family planning, mortality, and maternal and child health. Data collection was carried out in three phases from April 1992 to September 1993. THe NFHS is one of the most complete surveys of its kind ever conducted in India.
The households covered in the survey included 500,492 residents. The young age structure of the population highlights the momentum of the future population growth of the country; 38 percent of household residents are under age 15, with their reproductive years still in the future. Persons age 60 or older constitute 8 percent of the population. The population sex ratio of the de jure residents is 944 females per 1,000 males, which is slightly higher than sex ratio of 927 observed in the 1991 Census.
The primary objective of the NFHS is to provide national-level and state-level data on fertility, nuptiality, family size preferences, knowledge and practice of family planning, the potentiel demand for contraception, the level of unwanted fertility, utilization of antenatal services, breastfeeding and food supplemation practises, child nutrition and health, immunizations, and infant and child mortality. The NFHS is also designed to explore the demographic and socioeconomic determinants of fertility, family planning, and maternal and child health. This information is intended to assist policymakers, adminitrators and researchers in assessing and evaluating population and family welfare programmes and strategies. The NFHS used uniform questionnaires and uniform methods of sampling, data collection and analysis with the primary objective of providing a source of demographic and health data for interstate comparisons. The data collected in the NFHS are also comparable with those of the Demographic and Health Surveys (DHS) conducted in many other countries.
Kind of Data
Sample survey data
Unit of Analysis
- Data collected for women 13-49, indicators calculated for women 15-49
The National Family Health Survey 1992-1993 covers the following topics:
- HIV Knowledge
- Maternal Mortality
- Service Availability
The population covered by the 1992-93 DHS is defined as the universe of all women age 13-49 who were either permanent residents of the households in the NDHS sample or visitors present in the households on the night before the survey were eligible to be interviewed.
Producers and sponsors
International Institute for Population Sciences (IIPS)
Ministry of Health and Family Welfare (MOHFW)
East West Center/Macro International
United States Agency for International Development
The sample design for the NFHS was discussed during a Sample Design Workshop held in Madurai in Octber, 1991. The workshop was attended by representative from the PRCs; the COs; the Office of the Registrar General, India; IIPS and the East-West Center/Macro International. A uniform sample design was adopted in all the NFHS states. The Sample design adopted in each state is a systematic, stratified sample of households, with two stages in rural areas and three stages in urban areas.
SAMPLE SIZE AND ALLOCATION
The sample size for each state was specified in terms of a target number of completed interviews with eligible women. The target sample size was set considering the size of the state, the time and ressources available for the survey and the need for separate estimates for urban and rural areas of the stat. The initial target sample size was 3,000 completed interviews with eligible women for states having a population of 25 million or less in 1991; 4,000 completed interviews for large states with more than 25 million population; 8,000 for Uttar Pradesh, the largest state; and 1,000 each for the six small northeastern states. In States with a substantial number of backward districts, the initial target samples were increased so as to allow separate estimates to be made for groups of backward districts.
The urban and rural samples within states were drawn separetly and , to the extent possible, sample allocation was proportional to the size of the urban-rural populations (to facilitate the selection of a self-weighting sample for each state). In states where the urban population was not sufficiently large to provide a sample of at least 1,000 completed interviews with eligible women, the urban areas were appropriately oversampled (except in the six small northeastern states).
THE RURAL SAMPLE: THE FRAME, STRATIFICATION AND SELECTION
A two-stage stratified sampling was adopted for the rural areas: selection of villages followed by selection of households. Because the 1991 Census data were not available at the time of sample selection in most states, the 1981 Census list of villages served as the sampling frame in all the states with the exception of Assam, Delhi and Punjab. In these three states the 1991 Census data were used as the sampling frame.
Villages were stratified prior to selection on the basis of a number of variables. The firts level of stratification in all the states was geographic, with districts subdivided into regions according to their geophysical characteristics. Within each of these regions, villages were further stratified using some of the following variables : village size, distance from the nearest town, proportion of nonagricultural workers, proportion of the population belonging to scheduled castes/scheduled tribes, and female literacy. However, not all variables were used in every state. Each state was examined individually and two or three variables were selected for stratification, with the aim of creating not more than 12 strata for small states and not more than 15 strata for large states. Females literacy was often used for implicit stratification (i.e., the villages were ordered prior to selection according to the proportion of females who were literate). Primary sampling Units (PSUs) were selected systematically, with probaility proportional to size (PPS). In some cases, adjacent villages with small population sizes were combined into a single PSU for the purpose of sample selection. On average, 30 households were selected for interviewing in each selected PSU.
In every state, all the households in the selected PSUs were listed about two weeks prior to the survey. This listing provided the necessary frame for selecting households at the second sampling stage. The household listing operation consisted of preparing up-to-date notional and layout sketch maps of each selected PSU, assigning numbers to structures, recording addresses (or locations) of these structures, identifying the residential structures, and listing the names of the heads of all the households in the residentiak structures in the selected PSU. Each household listing team consisted of a lister and a mapper. The listing operation was supervised by the senior field staff of the concerned CO and the PRC in each state. Special efforts were made not to miss any household in the selected PSU during the listing operation. In PSUs with fewer than 500 households, a complete household listing was done. In PSUs with 500 or more households, segmentation of the PSU was done on the basis of existing wards in the PSU, and two segments were selected using either systematic sampling or PPS sampling. The household listing in such PSUs was carried out in the selected segments. The households to be interviewed were selected from provided with the original household listing, layout sketch map and the household sample selected for each PSU. All the selected households were approached during the data collection, and no substitution of a household was allowed under any circumstances.
THE RURAL URBAN SAMPLE: THE FRAME, STRATIFICATION AND SELECTION
A three-stage sample design was adopted for the urban areas in each state: selection of cities/towns, followed by urban blocks, and finally households. Cities and towns were selected using the 1991 population figures while urban blocks were selected using the 1991 list of census enumeration blocks in all the states with the exception of the firts phase states. For the first phase states, the list of urban blocks provided by the National Sample Survey Organization (NSSSO) served as the sampling frame.
All cities and towns were subdivided into three strata: (1) self-selecting cities (i.e., cities with a population large enough to be selected with certainty), (2) towns that are district headquaters, and (3) other towns. Within each stratum, the cities/towns were arranged according to the same kind of geographic stratification used in the rural areas. In self-selecting cities, the sample was selected according to a two-stage sample design: selection of the required number of urban blocks, followed by selection of households in each of selected blocks. For district headquarters and other towns, a three stage sample design was used: selection of towns with PPS, followed by selection of two census blocks per selected town, followed by selection of households from each selected block. As in rural areas, a household listing was carried out in the selected blocks, and an average of 20 households per block was selected systematically.
A total of 88,562 households were interviewed, two-thirds of which were rural. The overall household response rate -- 66 the number of households interviewed per 100 occupied households -- is 96 percent. The household response rate is slightly lower in urban areas (94 percent in rural areas (96 percent). The household response rate ranged between 92 and 98 percent in every state except Arunachal Pradesh, where the household response rate was 88 percent. In all, interviews were completed with 89,777 eligible women who slept in the household the night before the household interview. The individual response rate -- the number of completed interviews per 100 identified eligible women in the household -- was 96 percent in both urban and rural areas. The individual response rate ranged from 91 percent in Arunachal Pradesh to nearly 1000 percent in Nagaland. Most of the larger states had an individual response rate of more than 95 percent.
At the national level, the overall sampleweight for each household or woman is the product of the design weight for each (after adjustment for nonresponse) and the state weight. The calculation of the design weights at the state level is described in each state report.
Dates of Data Collection
Data Collection Mode
During the perdiod of data collection, IIPS assigned one Research Officer to the survey in most states for ensuring the use of correct survey procedures and maintaining the quality of the data. Throughout the survey, the staff from the CO, the PRC, and IIPS maintained close contact with all the teams through direct communication and spot-checking. The objectives was to provide support and advice to staff in the field and to enhance data quality and the efficiency of interviewers. This objective was accomplished by communicating data problems and possible solutions to the interviewing teams, reminding interviewers about proper probing techniques, and examining the work of the supervisors. In addition, data from the field were simultaneously entered into microcomputers, and field check tables were produced during the fieldwork to assess the quality of the data and to identify problem areas. These tables were discussed with the interviewing teams and supervisors during the fieldwork so that they could improve their performence if needed.
Data Collection Notes
In order to maintain uniform survey procedures acroos the states, four manuals dealing with different aspects of the survey were prepared at IIPS. The interviewer's Manual consists of instructions to the interviewers regarding interviewing techniques, field procedures, and instructions on the method of asking each question and recording answers. The manual for Field Editors and Supervisors contains a detailed description of the role of field editors and supervisors in the survey. A list of checks to be made by the field editor in the filled-in questionnaires is also provided in this manual. The Household listing Manual was meant for household listing teams, and contains procedures to be adopted for household listing. The guidelines for the training of the field staff are described in the manual entilted Training Guidelines.
The representatives of each of the COs and the PRCs were trained in a series of training of the Trainers Workshops organized by IIPS at the beginning of each phase of data collection. The purpose of these workshops was to ensure uniformity in data collection procedures in different states. Persons who were trained in each workshop subsequently trained the field staff in each state according to the standard procedures discussed in the training of trainers workshops. In thses workshops, detailed discussions were held on the objectives of the NFHS, different aspects of the survey, roles of various organizations participating in the survey, details of each of the three questionnaires used in the survey, methods of data collection and field supervision, and guidelines for the training of the field staff.
The fieldwork in each state was carried out by a number of interviewing teams, each team consisting of one field supervisor, one field editor and four interviewers. the number of interviewing teams in each state varied according to the sample size. In each state, interviewers were hired specially for the NFHS, taking into consideration their educational background, experience and other relevant qualifications. All interviewers were females, a stipulation that was necessary to ensure that women who were survey respondents would fell comfortable talking about topics which they may find somewhat sensistive.
Training of the entire field staff lasted for a minimum of 20 days in each state. The training course consisted of instruction in interviewing technicques and field procedures for the survey, a detailed review of each item in the questionnaire, instruction and practise in weighing and measuring children, mock interviews between participants in the classroom and practice interviews in the field. In addition two special lectures were arranged in each state one on the topic of family planning at the beginning of training on the section on contraception in the Woman's questionnaire, and one on maternal and child health practices, including immunizations, at the beginning of training was arranged for field editors and supervisors, which focused on the organization of fieldwork as well as methods of detecting errors in the field procedure and in the filled-in questionnaire.
Assignment of Primary Sampling Units (PSUs) to the teams and various logical decisions were made by the staff of each CO, who were designated as coordinators. In most cases, each team was allowed a fixed period of time to complete fieldwork in a PSU before moving to the next PSU. each interviewer was instructed not to conduct more than three individual interviews a day and was required to make a minimum of three callbacks if no suitable informant was available for the household interview or the eligible women identified in the selected household was not present at the time of household interview.
Tha main duty of field editor was to examine the completed questionnaires in the field for completeness, consistency and legibility of the information collected, and to ensure that all necessary corrections were made. Spacial attention was paid to missing information, skip instructions, filter questions, age information, and completeness of the birth history and the health section. If the problems were major, such as discrepancies between the birth history and the health section, the interviewers were required to revisit the respondent to correct the errors. If a return visit was not possible, the editors tried to establish, with the interviewer's assistance, the correct response. If either of these options was not possible, the editor designated the response as either "missing" or "inconsistent". An additional duty of the field editor was to obeserve ongoing interviews and verify the accuracy of the method of asking questions, recording answers, and following skip instructions correctly.
The field supervisor collected information on the village using the Village Questionnaire. In addition, the field supervisor conducted spot-checks to verify the accuracy of information collected on the eligibility of respondents.
Three types of questionnaires were used in the NFHS: the Household Questionnaire, the Women's Questionnaire, and the Village Questionnaire. The overall content and format of the questionnaires were determined in a Questionnaire Design Workshop held in Pune in September, 1991. The workshops were attended by representatives from all the PRCs, the Consulting Organizations, MOHFW, IIPS, other Indian organizations, USAID, and the East-West Center/macro Internationational. The contents and design of the questionnaires were based broadly on the DHS Model B Questionnaire, which is designed primarily for use in countries with low contraceptives prevalence. Keeping in the view the Indian sociocultural milieu and the objectives of the NFHS, additions and modifications were made to the model questionnaires after extensive deliberations at the workshop. In addition to a standard set of questions in all the states of the NFHS, it was decided at the workshop that individual states could recommend a number of state-specific questions which would be formulated after considering the issues of importance in each state. Based on the recommendations of this workshop, the questionnaires were finalized at IIPS, Bombay. The questionnaires are largely precoded, with fixed response categories.
A pretest of the questionnaires was carried out IIPS with the help of the PRC, Bhopal, in October, 1991. A 10-day training session for the interviewers and supervisors was conducted at the PRC. For the pretesting of the questionnaire, a total of 150 pretest interviews were completed in two villages near Bhopal and a few urban blocks within Bhopal city. After the pretest, appropriate changes were made in the questionnaires, based on the experience of the pretest. Questionnaires used in each state were bilingual, consisting of questions in both the state language and English. In each state, the entire content of the questionnaire was translated to the state language and then independently translated back to English. Appropriote changes were made in the translation of questions for which the back-translated version did not compare well with the original English version. The PRCs in these states undertook the responsibility of translating the questionnaires into the state language and pretesting the translated version of the questionnaires.
a) The Household Questionnaire was used to list all usual residents in each sample household plus any visitors who stayed in the household the night before the interview. Some basic information was collected on the characteristics of each person listed, including age, sex, marital status, education, occupation, and relationship to the head of the household, as well as health status? The main purpose of this section of the Household Questionnaires (Ever-married women age 13-49 years). In addition, the Household Questionnaire collected information on household conditions, such as the source of water, type of toilet facilities, materials used in the construction of the house, source of lighting, cooking fuel, ownership of agricultural land and livestock, ownership of various consumer durable goods, and characteristics of the head of the household such as religion, caste or tribe. The Household Questionnaire also included household birth and death records wherein all the live births and deaths that took place within the last two years in the household were recorded.
b) The Women's Questionnaire was used to collect information from eligible women - that is, all ever-married women, usual residents as well as visitors, age 13-49 years. The Woman's Questionnaire consisted of seven sections :
- Respondent's Background: Questions on age, marital status, caste/tribe, religion, education of the eligible woman are included. If the respondent is a vistir, information about her own household is also collected.
- Reproduction: In this section, information is collected about the births that a woman had during her life. The information collected includes the total number of sons and daughters that a woman has given birth to, information about stillbirths and aborations, a complete birth history (including month and year of birth, current age, sex, survival status, and if dead, age at death for each of live births), and information about current pregnancy and menstruations status.
- Contraception : This section collects information on the knowledge, ever use and current use of various family planning methods, intentions for future use, attitudes about family planning, exposure to family planning messages, and for current users, the duration of use, source of the method, and problems experiences with use.
- Health of Children: the question in this section realte to births in the year of the survey as well as to all the births in the previous four calendar years. The objective of this section is to obtain information related to the health of children. The topics included antenatal care, breastfeeding, vaccinations and recent illness of young children. The questions are organized into two subsections: section 4A containing questions on pregnancy and breastfeeding and section 4B containing questions on immunization and health of children.
- Fertility Preferences: this section gathers information on the desire for additional children, ideal family size and sex composition of children, preferred and ideal birth intervals, and husband's attitude about family size.
- Husband's background and Women's Work: Question related to age, education and work status of the husband as well as questions on the work status of the woman hearself are included.
- Height and Weight: the nutrinational status of children was measured using both weight and height/length of children under age 4 in most of the states.
c) The Village Questionnaire was used to collect information on all villages covered in the NFHS. The village Questionnaire included information on various amenities available in the villages such as electricity, water, transportation, and educationnal and health facilities.
In addition to the above standard questions used in all states of the NFHS, a set of state-specific questions was added in most of the states on issues of importance in thoses states. Accordingly, a set of questions on knowledge of AIDS was added to the NFHS in Arunachal, Pradesh, Assam, Delhi, Goa, Gujurat, Maharashtra, Manipur, Meghalaya, Mizoram, Nagaland, Tamil Nadu, TRipura, and west Bengal. The topics covered by state-specific questions in the other states are: dowry in Bihar, age at marriage in Rajasthan, sex preference for children in Uttar Pradesh, international migration in Kerala, Green Cards in Madhya Pradesh, benefits received from antipoverty programmes in Karnataka, and sex preselection and international migration in Penjab.
All completed questionnaires for the NFHS were sent for data processing to the office of the concerned CO. this process consisted of office editing, coding, data entry, and machine editing. Although field editors examined the completed questionnaires in the field, the questionnaires were re-edited at the CO by specially trained office editors. The office editors checked all skip sequences, all circled response codes, and information recorded in the filter questions. Special attention was paid to the consistency of responses to age questions and the accurate completion of the birth history. In the second stage of office editing, appropriate codes were assigned for the information on occupation, caste and cause of death, and commonly mentioned "other" responses were added to the coding scheme. One supervisor and four data entry operators were typically responsible for data entry and computer editing operations. For each state, the data were processed with four microcimputers using the data entry and editing software known as the Integrated System for Survey Analysis (ISSA). The data were entered directly from the precoded questionnaires, starting within one week of the receipt of the firt set of completed questionnaires. All data entry and editing operations were completed a few days after the end of fieldwork in each state. Computer-based checks were used to clean the data and remove inconsistencies. Age imputation was also completed at this stage. Age variables such as current age, age at first marriage, age of the woman when she started living with her husband, and the ages of all children were imputed for those cases in which information was missing or incoreect entries were detected.
Estimates of Sampling Error
The estimates from a sample survey are affected by two types of errors: (1) nonsampling errors, and (2) 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 first National Family Health Survey 1992-93 (NFHS) 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 NFHS 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 NFHS sample is the result of a multi-stage stratified design, and, consequently, it was necessary to use more complex formulae. The computer software used to calculate sampling errors for NFHS is the ISSA SAmpling Error Module (ISSAS). This module uses the Taylor linearization method for variance estimation , known as the CLUSTERS model, for survey estimates that are means or proportions. The Jackknife repeated replication method is used for variance estimation of more complex statistics such as total fertility rate and child mortality rates.
The Jackknife repeated replication method derives estimates of complex rates from each of several replications of the parent sample, and calculates standard errors for these estimates using simple formulae. Each replication considers all but one clusters in the calculation of the estimates.
In addition to the standard error, ISSAS 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. ISSAS also computes the relative error and confidence limits for the estimates.
Sampling errors for NFHS 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, and for the urban and rural areas.
Data and Data Related Resources
International Institute for Population Sciences (IIPS)
International Institute for Population Sciences (IIPS)
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