Demographic and Health Survey 2001
Nepal, 2001
Ministry of Health/New ERA
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Identification
Survey ID Number
NPL_2001_DHS_v01_M
Title
Demographic and Health Survey 2001
Country
| Name | Country code |
|---|---|
| Nepal | NPL |
Study type
Demographic and Health Survey (standard) - DHS IV
Series Information
The 2001 Nepal Demographic and Health Survey (NDHS) is the sixth in a series of national-level population and health surveys conducted in Nepal. It is the second nationally representative comprehensive survey conducted as part of the global Demographic and Health Survey (DHS) program, the first being the 1996 Nepal Family Health Survey (NFHS). The 2001 NDHS is the first in the history of demographic and health surveys conducted in Nepal that included a male sample.
Abstract
The 2001 Nepal Demographic and Health Survey (NDHS) is a nationally representative survey of 8,726 women age 15-49 and 2,261 men age 15-59. This Survey is the sixth in a series of national-level population and health surveys conducted in Nepal. It is the second nationally representative comprehensive survey conducted as part of the global Demographic and Health Survey (DHS) program, the first being the 1996 Nepal Family Health Survey (NFHS). The 2001 NDHS is the first in the history of demographic and health surveys conducted in Nepal that included a male sample. The 2001 NDHS was carried out under the aegis of the Family Health Division of the Department of Health Services, Ministry of Health, and was implemented by New ERA, a local research organization, which also conducted the 1996 NFHS. ORC Macro provided technical support through its MEASURE DHS+ project. The survey was funded by the United States Agency for International Development (USAID) through its mission in Nepal.
The principal objective of the 2001 NDHS is to provide current and reliable data on fertility and family planning, infant and child mortality, children's and women's nutritional status, the utilization of maternal and child health services, and knowledge of HIV/AIDS. This information is essential for informed policy decisions, planning, monitoring, and evaluation of programs on health in general and reproductive health in particular at both the national and regional levels.
A long-term objective of the survey is to strengthen the technical capacity of the Family Health Division of the Ministry of Health to plan, conduct, process, and analyze data from complex national population and health surveys. The 2001 NDHS data is comparable to data collected in the 1996 NFHS and similar to survey data conducted in other developing countries. This allows for temporal and spatial comparisons of demographic health information. The 2001 NDHS also adds to the vast and growing international database on demographic and health variables. The inclusion of data on men adds to the richness of this data.
The principal objective of the 2001 NDHS is to provide current and reliable data on fertility and family planning, infant and child mortality, children's and women's nutritional status, the utilization of maternal and child health services, and knowledge of HIV/AIDS. This information is essential for informed policy decisions, planning, monitoring, and evaluation of programs on health in general and reproductive health in particular at both the national and regional levels.
A long-term objective of the survey is to strengthen the technical capacity of the Family Health Division of the Ministry of Health to plan, conduct, process, and analyze data from complex national population and health surveys. The 2001 NDHS data is comparable to data collected in the 1996 NFHS and similar to survey data conducted in other developing countries. This allows for temporal and spatial comparisons of demographic health information. The 2001 NDHS also adds to the vast and growing international database on demographic and health variables. The inclusion of data on men adds to the richness of this data.
Kind of Data
Sample survey data
Unit of Analysis
- Household
- Women age 15-49
- Men age 15-59
- Women age 15-49
- Men age 15-59
Scope
Notes
The Nepal Demographic and Health Survey 2001 covers the following topics:
- Abortion
- Anthropometry
- Full Pregnancy History
- GPS/Georeferenced–Global Positioning System or Georeferenced Data
- HIV Knowledge
- Men's Survey
- Micronutrients
- Vitamin A Questions
- Women's Status–Questions: women's autonomy (household decisionmaking/free movement/access money) & Domestic violence
- Abortion
- Anthropometry
- Full Pregnancy History
- GPS/Georeferenced–Global Positioning System or Georeferenced Data
- HIV Knowledge
- Men's Survey
- Micronutrients
- Vitamin A Questions
- Women's Status–Questions: women's autonomy (household decisionmaking/free movement/access money) & Domestic violence
Coverage
Geographic Coverage
The 2001 NDHS collected demographic and health information from a nationally representative sample of ever-married women and men in the reproductive age groups of 15-49 and 15-59, respectively. The primary focus of the 2001 NDHS was to provide estimates of key population and health indicators, including fertility and mortality rates, for the country as a whole and for urban and rural areas separately.
Universe
The population covered by the 2008 DHS is defined as the universe of all women ever-married women and men in the reproductive age groups of 15-49 and 15-59
Producers and sponsors
Primary investigators
| Name |
|---|
| Ministry of Health/New ERA |
Producers
| Name | Role |
|---|---|
| ORC Macro | Technical assistance |
Funding Agency/Sponsor
| Name | Abbreviation | Role |
|---|---|---|
| United States Agency for International Development | USAID | Funding |
Sampling
Sampling Procedure
The survey was designed to obtain completed interviews of 8,400 ever-married women age 15-49. In addition, all ever-married males age 15-59 in every third household were interviewed. To take nonresponse into account, a total of 8,700 households nationwide were selected. The sample size was allocated to each district by urban and rural areas and the numbers of PSUs were calculated based on an average sample "take" (the number of ultimate sampled units in a cluster) of 34 completed interviews per PSU.
SAMPLE DESIGN
The 2001 NDHS collected demographic and health information from a nationally representative sample of ever-married women and men in the reproductive age groups of 15-49 and 15-59, respectively. The primary focus of the 2001 NDHS was to provide estimates of key population and health indicators, including fertility and mortality rates, for the country as a whole and for urban and rural areas separately. In addition, the sample was designed to provide estimates of most key variables for the 13 domains obtained by cross-classifying the three ecological zones (mountains, hills, and terai) with the five development regions (Eastern, Central, Western, Mid-western, and Far-western). Due to their small size, the mountain areas of the Western, Mid-western, and Far-western regions were combined.
SAMPLING FRAME
The 2001 NDHS used the sampling frame provided by the list of census enumeration areas (EAs) with population and household information from the 1991 Population Census. Administratively, Nepal is divided into 75 districts. Each district is subdivided into village development committees (VDCs), and each VDC is divided into wards. The primary sampling unit (PSU) for the 2001 NDHS is a ward or group of wards in rural areas and subwards in urban areas. In rural areas, the ward is small enough for a complete household listing, but in urban areas, the ward size is large. It was therefore necessary to subdivide each urban ward into subwards. Information on the subdivision of the urban wards was obtained from the Living Standards Measurement Survey, a project funded by the World Bank.
SAMPLE SELECTION
The sample for the survey is based on a two-stage, stratified, nationally representative sample of households. At the first stage of sampling, 257 PSUs - 42 in urban areas and 215 in rural areas were selected using systematic sampling with probability proportional to size. During fieldwork, six PSUs in the Mid-western region were dropped from the sample due to security issues, reducing the total number of PSUs covered to 251 and reducing the number of rural PSUs to 209. This also reduced the expected number of completed interviews to 8,170 from 8,400.
A complete household listing operation was then carried out in all the selected EAs to provide a sampling frame for the second-stage selection of households. Sketch maps were constructed to identify the relative position of housing units in an EA to help interviewers locate selected households during fieldwork. Table A.1 shows the sample distribution of PSUs.
Global positioning system (GPS) units were used to calculate latitude and longitude coordinates for each selected ward (or subward) during the household listing stage. One latitude/longitude coordinate was taken for the center of each settlement or community within the ward. The altitude reading was also taken with the GPS units. The positional accuracy of the GPS readings is approximately 5 to 10 meters for latitude/longitude and approximately 30 meters for altitude. This geographic information allows the 2001 NDHS data to be integrated into a geographic information system (GIS) along with other spatial data collected in the same localities and adds to the depth of information available from the 2001 NDHS.
At the second stage of sampling, systematic samples of 34 households per PSU on average were selected in all the regions in order to provide statistically reliable estimates of key demographic and health variables. However, since Nepal is predominantly rural, in order to obtain statistically reliable estimates for urban areas, it was necessary to oversample the urban areas. As such, the total sample is weighted and a final weighting procedure was applied to provide estimates for the different domains and for the urban and rural areas of the country as a whole.
SAMPLE DESIGN
The 2001 NDHS collected demographic and health information from a nationally representative sample of ever-married women and men in the reproductive age groups of 15-49 and 15-59, respectively. The primary focus of the 2001 NDHS was to provide estimates of key population and health indicators, including fertility and mortality rates, for the country as a whole and for urban and rural areas separately. In addition, the sample was designed to provide estimates of most key variables for the 13 domains obtained by cross-classifying the three ecological zones (mountains, hills, and terai) with the five development regions (Eastern, Central, Western, Mid-western, and Far-western). Due to their small size, the mountain areas of the Western, Mid-western, and Far-western regions were combined.
SAMPLING FRAME
The 2001 NDHS used the sampling frame provided by the list of census enumeration areas (EAs) with population and household information from the 1991 Population Census. Administratively, Nepal is divided into 75 districts. Each district is subdivided into village development committees (VDCs), and each VDC is divided into wards. The primary sampling unit (PSU) for the 2001 NDHS is a ward or group of wards in rural areas and subwards in urban areas. In rural areas, the ward is small enough for a complete household listing, but in urban areas, the ward size is large. It was therefore necessary to subdivide each urban ward into subwards. Information on the subdivision of the urban wards was obtained from the Living Standards Measurement Survey, a project funded by the World Bank.
SAMPLE SELECTION
The sample for the survey is based on a two-stage, stratified, nationally representative sample of households. At the first stage of sampling, 257 PSUs - 42 in urban areas and 215 in rural areas were selected using systematic sampling with probability proportional to size. During fieldwork, six PSUs in the Mid-western region were dropped from the sample due to security issues, reducing the total number of PSUs covered to 251 and reducing the number of rural PSUs to 209. This also reduced the expected number of completed interviews to 8,170 from 8,400.
A complete household listing operation was then carried out in all the selected EAs to provide a sampling frame for the second-stage selection of households. Sketch maps were constructed to identify the relative position of housing units in an EA to help interviewers locate selected households during fieldwork. Table A.1 shows the sample distribution of PSUs.
Global positioning system (GPS) units were used to calculate latitude and longitude coordinates for each selected ward (or subward) during the household listing stage. One latitude/longitude coordinate was taken for the center of each settlement or community within the ward. The altitude reading was also taken with the GPS units. The positional accuracy of the GPS readings is approximately 5 to 10 meters for latitude/longitude and approximately 30 meters for altitude. This geographic information allows the 2001 NDHS data to be integrated into a geographic information system (GIS) along with other spatial data collected in the same localities and adds to the depth of information available from the 2001 NDHS.
At the second stage of sampling, systematic samples of 34 households per PSU on average were selected in all the regions in order to provide statistically reliable estimates of key demographic and health variables. However, since Nepal is predominantly rural, in order to obtain statistically reliable estimates for urban areas, it was necessary to oversample the urban areas. As such, the total sample is weighted and a final weighting procedure was applied to provide estimates for the different domains and for the urban and rural areas of the country as a whole.
Response Rate
A total of 8,864 households were selected for the 2001 NDHS, of which 8,633 were found to be occupied. Household interviews were completed for 8,602 households or more than 99 percent of the occupied households. A total of 8,885 eligible women from these households and 2,353 eligible men from every third household were identified for the individual interviews. Interviews were successfully completed for 8,726 women and 2,261 men. The response rate for eligible women is slightly higher than for eligible men (98 percent and 96 percent, respectively).
Response rates for women and men vary by urban-rural residence. Rural women and especially men are slightly more likely than urban women and men to have completed an interview. There is little difference in the response rate among women by ecological zone, but men residing in the mountain region are more likely to have completed an interview (98 percent) than men residing in the hills (95 percent) and terai (96 percent).
Response rates for women and men vary by urban-rural residence. Rural women and especially men are slightly more likely than urban women and men to have completed an interview. There is little difference in the response rate among women by ecological zone, but men residing in the mountain region are more likely to have completed an interview (98 percent) than men residing in the hills (95 percent) and terai (96 percent).
Data Collection
Dates of Data Collection
| Start | End |
|---|---|
| 2001-01 | 2001-06 |
Data Collection Mode
Face-to-face
Supervision
The main fieldwork started in mid-January 2001 and lasted until the end of June. Throughout the survey, senior staff from the Ministry of Health, New ERA, USAID/Nepal, and ORC Macro maintained constant contact with the teams through direct communication and spot checking. To ensure high-quality data, teams were closely supervised through field visits, observations of interviews, and checking of completed questionnaires. In addition, the quality control team visited every team in the field to followup on the quality of the data collected. Data quality was also ensured by providing feedback to individual teams on the results of field check tables. These tables were computer generated at regular intervals from data obtained in the completed questionnaires. These results were discussed with the teams to improve their performance.
Data Collection Notes
A technical advisory committee was established and chaired by the director general of the Department of Health Services of the Ministry of Health to oversee the performance and activities of the 2001 NDHS. The committee was made up of the director of the Family Health Division of the Ministry of Health (vice-chairman) and other representatives from the Family Health Division, the Planning and Foreign Aid Division, and the Child Health Division of the Ministry of Health and representatives from the Ministry of Population and Environment, the National Planning Commission, the National Center for AIDS and STD Control, the National Health Education Information and Communication Center, the Parliament Secretariat, the Central Bureau of Statistics, the National Health Research Council, the Central Department of Population Studies at Tribhuvan University, New ERA, USAID/Nepal, and ORC Macro.
Training for the main survey was conducted in December 2000 and January 2001 in Kathmandu. A total of 79 field staff participated in the training. They were recruited for their language skills, academic qualifications, and previous survey work experience. Training was conducted mostly in Nepali, and practice sessions were conducted in all three local languages. The four-week training consisted of instruction in general interviewing techniques and field procedures for the survey, a detailed review of the questionnaires, practice in weighing and measuring women and children, mock interviews between participants in the classroom, and practice interviews in the field. In addition, special lectures were given on contraceptive knowledge and practice and the various methods used in Nepal, maternal and child health, and HIV/AIDS. A two-day training on anthropometric measurement was also given. A final selection of interviewers, editors, and supervisors was made based on their performance during the training. Persons selected to be supervisors and editors, and persons recruited for the quality control teams were given an additional two days of training in field supervision, editing and maintaining data quality in the field. At the end of the training, a total of 11 teams were constituted, comprising one male supervisor, one female editor, and one male and three female interviewers. In addition, one quality control team made up of three highly experienced individuals was constituted.
To maintain uniform survey procedures, four manuals on different aspects of the survey were prepared. The Interviewer's Manual discussed the objectives of the NDHS, interviewing techniques, field procedures, and general procedures for completing the questionnaires and included a detailed discussion of the Household, Women's, and Men's Questionnaires. The manual also contained information on how to weigh and measure women and children. The Supervisor's and Editor's Manual contained instructions on organizing and supervising fieldwork, maintaining and monitoring control sheets, and general rules for editing completed questionnaires and maintaining data quality. Trainers were given the Training Guidelines for DHS Surveys Manual, which describes the administrative and logistical aspects of training and data quality checks. The Household Listing Manual describes the mapping and household listing procedures used in DHS surveys.
The fieldwork was conducted from the fourth week of January to the end of June 2001.
Training for the main survey was conducted in December 2000 and January 2001 in Kathmandu. A total of 79 field staff participated in the training. They were recruited for their language skills, academic qualifications, and previous survey work experience. Training was conducted mostly in Nepali, and practice sessions were conducted in all three local languages. The four-week training consisted of instruction in general interviewing techniques and field procedures for the survey, a detailed review of the questionnaires, practice in weighing and measuring women and children, mock interviews between participants in the classroom, and practice interviews in the field. In addition, special lectures were given on contraceptive knowledge and practice and the various methods used in Nepal, maternal and child health, and HIV/AIDS. A two-day training on anthropometric measurement was also given. A final selection of interviewers, editors, and supervisors was made based on their performance during the training. Persons selected to be supervisors and editors, and persons recruited for the quality control teams were given an additional two days of training in field supervision, editing and maintaining data quality in the field. At the end of the training, a total of 11 teams were constituted, comprising one male supervisor, one female editor, and one male and three female interviewers. In addition, one quality control team made up of three highly experienced individuals was constituted.
To maintain uniform survey procedures, four manuals on different aspects of the survey were prepared. The Interviewer's Manual discussed the objectives of the NDHS, interviewing techniques, field procedures, and general procedures for completing the questionnaires and included a detailed discussion of the Household, Women's, and Men's Questionnaires. The manual also contained information on how to weigh and measure women and children. The Supervisor's and Editor's Manual contained instructions on organizing and supervising fieldwork, maintaining and monitoring control sheets, and general rules for editing completed questionnaires and maintaining data quality. Trainers were given the Training Guidelines for DHS Surveys Manual, which describes the administrative and logistical aspects of training and data quality checks. The Household Listing Manual describes the mapping and household listing procedures used in DHS surveys.
The fieldwork was conducted from the fourth week of January to the end of June 2001.
Data Collectors
| Name | Affiliation |
|---|---|
| New ERA | Family Health Division, Department of Health Services, Ministry of Health |
Questionnaires
Questionnaires
The 2001 NDHS used three questionnaires: the Household Questionnaire, the Women's Questionnaire, and the Men's Questionnaire. The content and design of the questionnaires were based on the MEASURE DHS+ Model 'B' Questionnaire. The questionnaires were specifically geared toward obtaining the kind of information needed by health and family planning program managers and policymakers. The model questionnaires were then adapted to local conditions and a number of additional questions specific to ongoing health and family planning programs in Nepal were added. These questionnaires were developed in English and translated into the three principal languages in use in the country: Nepali (the national language), Bhojpuri, and Maithili. They were then independently translated back to English and appropriate changes were made in the translation of questions in which the back-translated version did not compare well with the original English version. A pretest of all three questionnaires was conducted in the three local languages in September 2000.
a) All usual members in a selected household and visitors who stayed there the previous night were enumerated using the Household Questionnaire. Specifically, the Household Questionnaire obtained information on the relationship to the head of the household, residence, sex, age, marital status, and education of each usual resident or visitor. This information was used to identify eligible women and men for the individual interview. Ever-married women age 15-49 in all selected households and ever-married men age 15-59 in every third selected household, whether usual residents or visitors, were deemed eligible and were interviewed. The Household Questionnaire also obtained information on some basic socioeconomic indicators such as the source of drinking water, the type of toilet facilities, the ownership of a variety of consumer durable items, and the flooring material. All eligible women and all children born since Baisakh 2052 in the Nepali calendar (which roughly corresponds to April 1995 in the Gregorian calendar) were weighed and measured.
b) The Women's Questionnaire collected information on female respondent's background characteristics; reproductive history; contraceptive knowledge and use; antenatal, delivery, and postnatal care; infant feeding practices; child immunization and health; marriage; fertility preferences; attitudes about family planning; husband's background characteristics; women's work; and knowledge of HIV/AIDS.
c) The Men's Questionnaire collected information on the male respondent's background characteristics, contraceptive knowledge and use, marriage, fertility preferences, attitudes about family planning, and knowledge of HIV/AIDS.
a) All usual members in a selected household and visitors who stayed there the previous night were enumerated using the Household Questionnaire. Specifically, the Household Questionnaire obtained information on the relationship to the head of the household, residence, sex, age, marital status, and education of each usual resident or visitor. This information was used to identify eligible women and men for the individual interview. Ever-married women age 15-49 in all selected households and ever-married men age 15-59 in every third selected household, whether usual residents or visitors, were deemed eligible and were interviewed. The Household Questionnaire also obtained information on some basic socioeconomic indicators such as the source of drinking water, the type of toilet facilities, the ownership of a variety of consumer durable items, and the flooring material. All eligible women and all children born since Baisakh 2052 in the Nepali calendar (which roughly corresponds to April 1995 in the Gregorian calendar) were weighed and measured.
b) The Women's Questionnaire collected information on female respondent's background characteristics; reproductive history; contraceptive knowledge and use; antenatal, delivery, and postnatal care; infant feeding practices; child immunization and health; marriage; fertility preferences; attitudes about family planning; husband's background characteristics; women's work; and knowledge of HIV/AIDS.
c) The Men's Questionnaire collected information on the male respondent's background characteristics, contraceptive knowledge and use, marriage, fertility preferences, attitudes about family planning, and knowledge of HIV/AIDS.
Data Processing
Data Editing
The completed questionnaires were returned to the New ERA office in Kathmandu for data processing. The office editing staff first checked that questionnaires for all selected households and eligible respondents had been received from the field. In addition, the few questions that had not been precoded (example, occupation, ethnicity) were coded at this time. The data were then entered and edited using microcomputers and the new software CSPro, developed jointly by ORC Macro, the U.S. Bureau of Census, and SerPro Ltda. Office editing and data processing activities were initiated soon after the beginning of fieldwork and were completed by mid-July.
Data Appraisal
Estimates of Sampling Error
Sampling errors, on the other hand, can be evaluated statistically. The sample of respondents selected in the 2001 NDHS 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 formulae for calculating sampling errors. However, the 2001 NDHS sample is the result of a multistage stratified design, and consequently, it was necessary to use more complex formulae. The computer software used to calculate sampling errors for the 2001 NDHS is the ISSA Sampling Error Module (ISSAS). 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.
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 cluster in the calculation of the estimates. Pseudo-independent replications are thus created. In the 2001 NDHS, there were 251 nonempty clusters (PSUs). Hence, 251 replications were created.
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 the 2001 NDHS 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 the three ecological zones (mountains, hills, and terai), and for each of the 13 subdomains in the country. 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. Tables B.2 to B.4 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 DEFT is considered undefined when the standard error considering simple random sample is zero (when the estimate is close to 0 or 1).
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 “currently using any contraceptive method” for currently married women age 15-49, the relative standard errors as a percentage of the estimated mean for the whole country, for urban areas, and for rural areas are 2.8 percent, 3.2 percent, and 3.2 percent, respectively.
The confidence interval (e.g., as calculated for “currently using any contraceptive method” for currently married women age 15-49) can be interpreted as follows: the overall national sample proportion is 0.393 and its standard error is 0.011. Therefore, to obtain the 95 percent confidence limits, one adds and subtracts twice the standard error to the sample estimate, i.e. 0.393±2(0.011). There is a high probability (95 percent) that the true average proportion of contraceptive use for currently married women age 15-49 is between 0.371 and 0.415.
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 formulae for calculating sampling errors. However, the 2001 NDHS sample is the result of a multistage stratified design, and consequently, it was necessary to use more complex formulae. The computer software used to calculate sampling errors for the 2001 NDHS is the ISSA Sampling Error Module (ISSAS). 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.
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 cluster in the calculation of the estimates. Pseudo-independent replications are thus created. In the 2001 NDHS, there were 251 nonempty clusters (PSUs). Hence, 251 replications were created.
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 the 2001 NDHS 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 the three ecological zones (mountains, hills, and terai), and for each of the 13 subdomains in the country. 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. Tables B.2 to B.4 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 DEFT is considered undefined when the standard error considering simple random sample is zero (when the estimate is close to 0 or 1).
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 “currently using any contraceptive method” for currently married women age 15-49, the relative standard errors as a percentage of the estimated mean for the whole country, for urban areas, and for rural areas are 2.8 percent, 3.2 percent, and 3.2 percent, respectively.
The confidence interval (e.g., as calculated for “currently using any contraceptive method” for currently married women age 15-49) can be interpreted as follows: the overall national sample proportion is 0.393 and its standard error is 0.011. Therefore, to obtain the 95 percent confidence limits, one adds and subtracts twice the standard error to the sample estimate, i.e. 0.393±2(0.011). There is a high probability (95 percent) that the true average proportion of contraceptive use for currently married women age 15-49 is between 0.371 and 0.415.
Data Appraisal
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 2001 NDHS to minimize this type of error, nonsampling errors are impossible to avoid and difficult to evaluate statistically.
Access policy
Access authority
| Name | Affiliation | URL | |
|---|---|---|---|
| MEASURE DHS | ICF International | archive@measuredhs.com | www.measuredhs.com |
Contacts
| Name | URL | |
|---|---|---|
| General Inquiries | info@measuredhs.com | www.measuredhs.com |
| Data and Data Related Resources | archive@measuredhs.com | www.measuredhs.com |
Citation requirements
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
- 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
Disclaimer
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.