Demographic and Health Survey 1987
Sri Lanka, 1987
Get Microdata
Reference ID
LKA_1987_DHS_v01_M
Producer(s)
Department of Census and Statistics (DCS)
Created on
Dec 20, 2012
Last modified
Mar 29, 2019
Page views
26655
Downloads
245
Identification
Survey ID Number
LKA_1987_DHS_v01_M
Title
Demographic and Health Survey 1987
Country
| Name | Country code |
|---|---|
| Sri Lanka | LKA |
Study type
Demographic and Health Survey (standard) - DHS I
Series Information
The Sri Lanka Demographic and Health Survey 1987 is the first survey of its kind in Sri Lanka.
Abstract
The Demographic and Health Survey (DHS) is an important link in a chain of surveys carried out in Sri Lanka in the past decade or so. Having been designed as part of an international survey program and modelled on the lines of the well renowned World Fertility Survey (WFS) program, the DHS provides an exceptionally valuable source of data for the estimation of trends over time within Sri Lanka as well as for cross national comparison.
The survey focussed primarily on fertility, contraception and child mortality as did WFS but. also measured several indicators of child health, particularly immunization coverage and nutrition status. The inclusion of health sector information has been welcome and fruitful, for improve- ment of nutrition status is a subject to which the Government of Sri Lanka has accorded high priority.
The Sri Lanka Demographic and Health Survey has the following objectives:
1. To provide policymakers and administrators with current and accurate data on fertility, morbidity, family planning and selected indicators of health status which could be used for planning new strategies for the wellbeing of the population; etc.
2. To provide data which can be used to analyze trends over time. The SLDHS examines many of the same fertility, mortality, and health issues that were addressed in earlier surveys, most notably the SLWFS and the more recent SLCPS; and
3. To add to the international body of data which can be used for comparative studies.
The survey focussed primarily on fertility, contraception and child mortality as did WFS but. also measured several indicators of child health, particularly immunization coverage and nutrition status. The inclusion of health sector information has been welcome and fruitful, for improve- ment of nutrition status is a subject to which the Government of Sri Lanka has accorded high priority.
The Sri Lanka Demographic and Health Survey has the following objectives:
1. To provide policymakers and administrators with current and accurate data on fertility, morbidity, family planning and selected indicators of health status which could be used for planning new strategies for the wellbeing of the population; etc.
2. To provide data which can be used to analyze trends over time. The SLDHS examines many of the same fertility, mortality, and health issues that were addressed in earlier surveys, most notably the SLWFS and the more recent SLCPS; and
3. To add to the international body of data which can be used for comparative studies.
Kind of Data
Sample survey data
Unit of Analysis
- Household
- Women age 15-49
- Women age 15-49
Scope
Notes
The Sri Lanka Demographic and Health Survey 1987 covers the following topics:
- Anthropometry
- Birth Registration
- Contraception
- Child health
- Health
- Marriage and migration
- Fertility preferences
- Anthropometry
- Birth Registration
- Contraception
- Child health
- Health
- Marriage and migration
- Fertility preferences
Coverage
Geographic Coverage
National
Universe
In principle, the sample was designed to cover private households in the areas sampled. The population residing in institutions and institutional households was excluded. For the detailed individual interview, the eligibility criteria were: ever-married women aged 15 through 49 who slept in the household the previous night.
Producers and sponsors
Primary investigators
| Name | Affiliation |
|---|---|
| Department of Census and Statistics (DCS) | Ministry of Plan Implementation |
Producers
| Name | Affiliation | Role |
|---|---|---|
| Institute for Resource Development | Westinghouse | Technical assistance |
Funding Agency/Sponsor
| Name | Abbreviation | Role |
|---|---|---|
| U.S. Agency for International Development | USAID | Funding |
Sampling
Sampling Procedure
SURVEY SAMPLE DESIGN
On the basis of socio-economic and ecological criteria, and the experience of the SLWFS, nine zones were created. It was felt that some of the six SLWFS zones were too heterogeneous and should be redrawn as shown in Figure i.i and described below:
Zone 1 - Colombo Metropolitan area consisting of SLWFS zone 1 and parts of zone 2.
Zone 2 - Colombo feeder areas and Northern part of SLWFS zone 2.
Zone 3 - South Western coastal low lands corresponding to Southern part of SLWFS zone 2.
Zone 4 - Lower South Central hill country corresponding to Western and Southern part of SLWFS zone 6, excluding districts with a concentration of estates.
Zone 5 - South Central hill country corresponding to part of SLWFS zone 5 with a concentration of estates.
Zone 6 - Irrigated Dry Zone corresponding to SLWFS zone 3, with major or minor irrigation schemes.
Zone 7 - Rain fed Dry Zone covering the rest of SLWFS zone 3.
Zone 8 - Eastern Coastal Belt, corresponding to SLWFS zone 4 (not included in SLDNS).
Zone 9 - Northern Province corresponding to SLWFS zone 5 (not included in SLDHS).
The changes SLDHS made to the SLWFS zones were designed: a) to separate the Colombo urban feeder areas from rural hinterlands; b) to separate rural areas with predominantly estate populations from other rural areas; and c) to distinguish between irrigated dry zone areas which are new settlements under development projects from those areas which rely primarily on rains for cultivation.
Although the survey originally planned to conduct interviews in all nine zones, Civil disturbances in zones 9 and 8 (the Northern and Eastern provinces) prevented interviews from being conducted there. These zones, which contain approximately 14 percent of the 1986 estimated population of Sri Lanka, have been excluded from the SLDHS.
With the exception of zone 5, the sample was allocated equally between zones with an estimated target 900 completed individual interviews per zone. Zone 5 was given a larger target sample size of 1,350 to permit over sampling of the estate plantation workers.
In principle, the sample was designed to cover private households in the areas sampled. The population residing in institutions and institutional households was excluded. For the detailed individual interview, the eligibility criteria were: ever-married women aged 15 through 49 who slept in the household the previous night.
For the selection of area units, the sample frame was based on block statistics from the 1981 Census of Population and Housing. However, these figures were updated where possible on the basis of the work done in connection with a 1985-86 labour force survey. This applied in particular to newly settled areas with the development of irrigation schemes in the dry zone. For the final selection of housing units within ultimate area units, a special operation was undertaken before the survey to update household lists within selected census blocks.
The zones created by the SLDHS, which were designed to capture relatively homogeneous subgroups of the population, served as the primary strata. Each zone was further stratified into (up to) three strata: urban, rural, and estate areas. Further implicit stratification was achieved by ordering the sampling areas according to administrative and geographical location. Similar systematic sampling procedures were followed at all stages up to and including the selection of housing units.
The sampling of housing units was undertaken in two or three stages depending upon the stratum. In densely populated zones i, 2, and 3, and in urban strata of all zones a three stage design was used:
At the first stage, a stratified sample of Gram Savaka or equivalent areas (waras or estates) with probability proportional to size (PPS) was selected. The number of primary sampling units (PSIs) selected was 54 in zones 5 and 36 in each of the other zones. Within a given zone, the number to be selected in a stratum was allocated proportionately to the strata populations.
1.Within each PSU, two census blocks were selected with PPS, systematically without replacement.
2.The final stage consisted of the selection of the housing units in selected blocks with inverse PPS so as to yield a self weighting sample within each stratum.
For the main survey, there was no further sampling as all eligible women in each selected housing unit were taken into the sample. Also, for the anthropometric measurements, all children 3 through 36 months of eligible women were taken.
In the non-urban strata in zones 3 through 7, the only difference in procedures was that generally only one block was selected per PSU. This procedure effectively reduced the number of stages to two: blocks as the first stage and housing units as the second stage.
Since zones were allocated generally uniform sample sizes, the overall sampling fractions varied in inverse proportion to the zone population.
On the basis of socio-economic and ecological criteria, and the experience of the SLWFS, nine zones were created. It was felt that some of the six SLWFS zones were too heterogeneous and should be redrawn as shown in Figure i.i and described below:
Zone 1 - Colombo Metropolitan area consisting of SLWFS zone 1 and parts of zone 2.
Zone 2 - Colombo feeder areas and Northern part of SLWFS zone 2.
Zone 3 - South Western coastal low lands corresponding to Southern part of SLWFS zone 2.
Zone 4 - Lower South Central hill country corresponding to Western and Southern part of SLWFS zone 6, excluding districts with a concentration of estates.
Zone 5 - South Central hill country corresponding to part of SLWFS zone 5 with a concentration of estates.
Zone 6 - Irrigated Dry Zone corresponding to SLWFS zone 3, with major or minor irrigation schemes.
Zone 7 - Rain fed Dry Zone covering the rest of SLWFS zone 3.
Zone 8 - Eastern Coastal Belt, corresponding to SLWFS zone 4 (not included in SLDNS).
Zone 9 - Northern Province corresponding to SLWFS zone 5 (not included in SLDHS).
The changes SLDHS made to the SLWFS zones were designed: a) to separate the Colombo urban feeder areas from rural hinterlands; b) to separate rural areas with predominantly estate populations from other rural areas; and c) to distinguish between irrigated dry zone areas which are new settlements under development projects from those areas which rely primarily on rains for cultivation.
Although the survey originally planned to conduct interviews in all nine zones, Civil disturbances in zones 9 and 8 (the Northern and Eastern provinces) prevented interviews from being conducted there. These zones, which contain approximately 14 percent of the 1986 estimated population of Sri Lanka, have been excluded from the SLDHS.
With the exception of zone 5, the sample was allocated equally between zones with an estimated target 900 completed individual interviews per zone. Zone 5 was given a larger target sample size of 1,350 to permit over sampling of the estate plantation workers.
In principle, the sample was designed to cover private households in the areas sampled. The population residing in institutions and institutional households was excluded. For the detailed individual interview, the eligibility criteria were: ever-married women aged 15 through 49 who slept in the household the previous night.
For the selection of area units, the sample frame was based on block statistics from the 1981 Census of Population and Housing. However, these figures were updated where possible on the basis of the work done in connection with a 1985-86 labour force survey. This applied in particular to newly settled areas with the development of irrigation schemes in the dry zone. For the final selection of housing units within ultimate area units, a special operation was undertaken before the survey to update household lists within selected census blocks.
The zones created by the SLDHS, which were designed to capture relatively homogeneous subgroups of the population, served as the primary strata. Each zone was further stratified into (up to) three strata: urban, rural, and estate areas. Further implicit stratification was achieved by ordering the sampling areas according to administrative and geographical location. Similar systematic sampling procedures were followed at all stages up to and including the selection of housing units.
The sampling of housing units was undertaken in two or three stages depending upon the stratum. In densely populated zones i, 2, and 3, and in urban strata of all zones a three stage design was used:
At the first stage, a stratified sample of Gram Savaka or equivalent areas (waras or estates) with probability proportional to size (PPS) was selected. The number of primary sampling units (PSIs) selected was 54 in zones 5 and 36 in each of the other zones. Within a given zone, the number to be selected in a stratum was allocated proportionately to the strata populations.
1.Within each PSU, two census blocks were selected with PPS, systematically without replacement.
2.The final stage consisted of the selection of the housing units in selected blocks with inverse PPS so as to yield a self weighting sample within each stratum.
For the main survey, there was no further sampling as all eligible women in each selected housing unit were taken into the sample. Also, for the anthropometric measurements, all children 3 through 36 months of eligible women were taken.
In the non-urban strata in zones 3 through 7, the only difference in procedures was that generally only one block was selected per PSU. This procedure effectively reduced the number of stages to two: blocks as the first stage and housing units as the second stage.
Since zones were allocated generally uniform sample sizes, the overall sampling fractions varied in inverse proportion to the zone population.
Deviations from the Sample Design
It is important to note once again that the districts in the northern and eastern portions of the country were not covered by the SLDHS because of civil disturbances. Whenever comparisons are made between the SLDHS and the earlier SLWFS and SLCPS, the differences in areas covered by the surveys should be kept in mind.
Response Rate
A total of 8,119 households were listed in seven zones. Not all of these turned out to be valid households in the field and the completion rate (response rate) at the household level was 96.3 percent. From these households, 6,170 eligible respondents were identified and interviews were completed among 5,865 ever-married women for a response rate of 95.1 percent.
It is important to note once again that the districts in the northern and eastern portions of the country were not covered by the SLDHS because of civil disturbances. Whenever comparisons are made between the SLDHS and the earlier SLWFS and SLCPS, the differences in areas covered by the surveys should be kept in mind.
It is important to note once again that the districts in the northern and eastern portions of the country were not covered by the SLDHS because of civil disturbances. Whenever comparisons are made between the SLDHS and the earlier SLWFS and SLCPS, the differences in areas covered by the surveys should be kept in mind.
Weighting
The overall average sampling fraction is 3.95 per thousand. The sampling weights applied in the analysis are inversely proportional to the above fractions, with a further modification for household and individual non-response.
The sample was designed to be self-weighting within strata as well as across strata within a given zone (with the exception of the estate area in zone 5 which was over sampled).
The sample was designed to be self-weighting within strata as well as across strata within a given zone (with the exception of the estate area in zone 5 which was over sampled).
Data Collection
Dates of Data Collection
| Start | End |
|---|---|
| 1987-01 | 1987-03 |
Data Collection Mode
Face-to-face
Supervision
For the purpose of coordinating the field work and implementing quality control procedures, five field coordinators were appointed. The coordinators visited the interviewers in the field and reviewed questionnaires completed by each interviewer both at the beginning and midstream of field work.
Data Collection Notes
The field staff for the survey were drawn from among Statistical Investigators of the DCS, the majority of whom had field experience in previous fertility surveys such as the SLWFS and SLCPS. Nine survey teams were formed. A team consisted of four to seven female interviewers and a supervisor for a total of 48 interviewers and 9 supervisors (5 female and 4 male). In addition, 18 measurers collected length and weight data from children 3 through 36 months of age. A measurer and assistant measurer accompanied each team of interviewers. The interviewers, supervisors, and measurers were trained in January 1987 for I0 days. The measurers were given a standardization test by an experienced nutritionist immediately following their training and again midway through field data collection.
The training for the interviewers was conducted over a period of two weeks and consisted primarily of role playing sessions and other exercises deigned to familiarize them with the questionnaire. In addition, each interviewer completed at least three practice interviews in the field. All the supervisors had previously been involved with the SLWFS and/or the SLCPS. Among the interviewers, about three-fourths had experience conducting interviews for SLWFS and/or SLCPS. During the first week of data collection, all new interviewers were teamed with an experienced interviewer and two questionnaires were completed for each respondent. The questionnaire from the new interviewer was then compared against the questionnaire completed by the experienced person and necessary corrections made. This procedure provided additional on the job training for new interviewers and helped to build their confidence. The training of heights and weights measurers and assistants was carried out with special care as this was the first experience with anthropometric measurements for the survey staff. The training was conducted by a specialist from IRD Westinghouse and followed guidelines developed by the United Nations (United Nations Department of Technical Co-operation for Development Statistical office, New York 1986).
The 18 measurers and assistants participated in the relevant training sessions for the interviewers. In addition, for over a week, they received practical instruction outside the classroom in the techniques of taking accurate height and weight measurements of children. Practice sessions were conducted at two children's homes in Colombo. At the completion of the training period all measurers were given a test which consisted of all trainees and the supervisor measuring a group of i0 children twice. The measurements were graded for precision (the ability to record the same measurement twice on the same child) and for accuracy (the closeness of the reading to that of the supervisor). One of the measurers failed to pass the test and was assigned to other survey duties. To ensure that standards were maintained throughout the field work, the test was readministered midway through field work. Analysis of the test data indicated that 55 percent of the measurers overestimated length, 29 percent underestimated and 16 percent showed no variation from the supervisor's measurements. The average error among those who underestimated length was 2.7 millimeters. The average error among those who overestimated length was 1.9 millimeters. During the test, 91 percent of the children were measured to within half a centimeter of the supervisor's measurement.
Data collection began January 18, 1987, and was essentially completed by the end of March except for a few areas which began late and were completed by May. Each questionnaire was edited in the field during the evening following the interview. In addition, all questionnaires were further reviewed and edited in Colombo.
All survey activities were completed on schedule and within a relatively short period of time from October 1986 to March 1988. The calender of activities is shown below:
- Survey design Oct 1986
- Questionnaire design and translation Nov 1986
- Preparation of manuals Oct to Nov 1986
- Pretest of questionnaires Nov 1986
- Selection of field staff Dec 1986
- Questionnaire and manual printing Dec 1986
- Supervisor, interviewer, and measurers training Jan 1987
- Field work Jan to April 1987
- Data processing and editing Feb to May 1987
- Tabulations July to August 1987
- Preparation of preliminary report August 1987
- Preparation of draft final report September to Nov 1987
- Seminar on principal findings November 1987
- Preparation of final report Dec 1987 to March 1988
The training for the interviewers was conducted over a period of two weeks and consisted primarily of role playing sessions and other exercises deigned to familiarize them with the questionnaire. In addition, each interviewer completed at least three practice interviews in the field. All the supervisors had previously been involved with the SLWFS and/or the SLCPS. Among the interviewers, about three-fourths had experience conducting interviews for SLWFS and/or SLCPS. During the first week of data collection, all new interviewers were teamed with an experienced interviewer and two questionnaires were completed for each respondent. The questionnaire from the new interviewer was then compared against the questionnaire completed by the experienced person and necessary corrections made. This procedure provided additional on the job training for new interviewers and helped to build their confidence. The training of heights and weights measurers and assistants was carried out with special care as this was the first experience with anthropometric measurements for the survey staff. The training was conducted by a specialist from IRD Westinghouse and followed guidelines developed by the United Nations (United Nations Department of Technical Co-operation for Development Statistical office, New York 1986).
The 18 measurers and assistants participated in the relevant training sessions for the interviewers. In addition, for over a week, they received practical instruction outside the classroom in the techniques of taking accurate height and weight measurements of children. Practice sessions were conducted at two children's homes in Colombo. At the completion of the training period all measurers were given a test which consisted of all trainees and the supervisor measuring a group of i0 children twice. The measurements were graded for precision (the ability to record the same measurement twice on the same child) and for accuracy (the closeness of the reading to that of the supervisor). One of the measurers failed to pass the test and was assigned to other survey duties. To ensure that standards were maintained throughout the field work, the test was readministered midway through field work. Analysis of the test data indicated that 55 percent of the measurers overestimated length, 29 percent underestimated and 16 percent showed no variation from the supervisor's measurements. The average error among those who underestimated length was 2.7 millimeters. The average error among those who overestimated length was 1.9 millimeters. During the test, 91 percent of the children were measured to within half a centimeter of the supervisor's measurement.
Data collection began January 18, 1987, and was essentially completed by the end of March except for a few areas which began late and were completed by May. Each questionnaire was edited in the field during the evening following the interview. In addition, all questionnaires were further reviewed and edited in Colombo.
All survey activities were completed on schedule and within a relatively short period of time from October 1986 to March 1988. The calender of activities is shown below:
- Survey design Oct 1986
- Questionnaire design and translation Nov 1986
- Preparation of manuals Oct to Nov 1986
- Pretest of questionnaires Nov 1986
- Selection of field staff Dec 1986
- Questionnaire and manual printing Dec 1986
- Supervisor, interviewer, and measurers training Jan 1987
- Field work Jan to April 1987
- Data processing and editing Feb to May 1987
- Tabulations July to August 1987
- Preparation of preliminary report August 1987
- Preparation of draft final report September to Nov 1987
- Seminar on principal findings November 1987
- Preparation of final report Dec 1987 to March 1988
Data Collectors
| Name | Abbreviation | Affiliation |
|---|---|---|
| Department of Census and Statistics | DCS | Ministry of Plan Implementation |
Questionnaires
Questionnaires
The Sri Lanka Demographic and Health Survey used two questionnaires each of which was pretested.
a) The first, called the Household Questionnaire, was used to list all usual household members and any visitors who slept in the household the preceding night. For each person listed, information on age, sex, and marital status and whether or not he/she slept in the household the previous night was recorded. From this list eligible respondents were selected for interview. An eligible respondent is defined as a woman currently married, divorced, separated, or widowed between the ages of 15 and 49 who slept in the household the previous night.
b) The second or Individual Questionnaire was administered to each eligible respondent. On the average, an individual interview took approximately 35 to 40 minutes. The Individual Questionnaire consisted of nine sections:
1. Respondents background
2. Birth history-dates of all live births and infant and child deaths
3. Contraception-knowledge, ever use, current use and a detailed history of inter birth use in the last 5 years
4. Child health -immunization status, episodes of diarrhea, breastfeeding, the use of supplementary foods, prenatal care, and assistance at delivery
5. Marriage and migration
6. Fertility preferences
7. Husband's background and respondent's work
8. Socio-economic indicators
9. Length and weight-measurements of all children 3 through 36 months.
More than in similar fertility and family planning surveys conducted in the past, the SLDHS devoted considerable time and attention to obtaining information on the health status of mothers and children. In addition to many health related questions, anthropometric length and weight measurements were taken on all children 3 months through 36 months.
a) The first, called the Household Questionnaire, was used to list all usual household members and any visitors who slept in the household the preceding night. For each person listed, information on age, sex, and marital status and whether or not he/she slept in the household the previous night was recorded. From this list eligible respondents were selected for interview. An eligible respondent is defined as a woman currently married, divorced, separated, or widowed between the ages of 15 and 49 who slept in the household the previous night.
b) The second or Individual Questionnaire was administered to each eligible respondent. On the average, an individual interview took approximately 35 to 40 minutes. The Individual Questionnaire consisted of nine sections:
1. Respondents background
2. Birth history-dates of all live births and infant and child deaths
3. Contraception-knowledge, ever use, current use and a detailed history of inter birth use in the last 5 years
4. Child health -immunization status, episodes of diarrhea, breastfeeding, the use of supplementary foods, prenatal care, and assistance at delivery
5. Marriage and migration
6. Fertility preferences
7. Husband's background and respondent's work
8. Socio-economic indicators
9. Length and weight-measurements of all children 3 through 36 months.
More than in similar fertility and family planning surveys conducted in the past, the SLDHS devoted considerable time and attention to obtaining information on the health status of mothers and children. In addition to many health related questions, anthropometric length and weight measurements were taken on all children 3 months through 36 months.
Data Processing
Data Editing
Data were entered onto microcomputers starting just two weeks after the commencement of field work. The ISSA (Integrated System for Survey Analysis) software package of programs developed by IRD/Westinghouse was used for data entry, machine editing, and tabulation. An especially effective procedure for correcting errors and inconsistencies detected during office editing and data entry was to relay information about problems in a questionnaire to the interviewers while they were still in the field. In most cases the problem could be corrected by going back to a respondent. As a result of this procedure, field errors diminished considerabiy With time end the volume af editing was reduced to a minimal level.
Data Appraisal
Estimates of Sampling Error
The results from sample surveys are affected by two types of errors: (1) nonsampling error and (2) sampling error. Nonsampling error is due to mistakes made in carrying out field activities, such as failure to locate and interview the correct h0usehold, errors in the way questions are asked, misunderstanding of the questions on the part of either the interviewer or the respondent, data entry errors, etc. Although efforts were made during the design and implementation of the Sri Lanka Demographic and Health Survey to minimize this type of error, nonsampling errors are impossible to avoid entirely and difficult to evaluate statistically.
Sampling errors, on the other hand, can be evaluated statistically. The sample of women ~selected in the SLDHS is only one of many samples of the same size that could have been selected from the same population, using the same design. Each one of these samples would have yielded results somewhat different from the sample that was actually selected. The variability observed between all possible samples constitutes sampling error, which, although it is not known exactly, can be estimated from the survey results.
Sampling error is usually measured in terms of the "standard error" of a particular statistic (mean, percentage, etc.), which is the square root of the variance of the statistic across all possible samples of equal size and design. The standard error can be used to calculate confidence intervals within which one can be reasonably sure the true value of the variable for the whole population falls. For example, for any given statistic calculated from a sample survey, the value of that same statistic as measured in 95 percent of all possible samples of identical size and design will fall within a range of plus or minus two times the standard error of that statistic.
If simple random sampling had been used to select women for the SLDHS, it would have been possible to use straightforward formulas for calculating sampling errors. However, the SLDHS sample design depended on stratification, stages, and clusters and consequently, it was necessary to utilize more complex formulas. The computer package CLUSTERS was used to assist in computing the sampling errors with the proper statistical methodology.
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 one indicates that the sample design is as efficient as a simple random sample and a value greater than one indicates the increase in the sampling error due to the use of a more c0mplex and less statistically efficient design.
Sampling errors are presented in Table A.1 of the survey Final Report for 32 variables considered to be of major interest. Results are presented for the whole country, for urban and rural areas, for three age groups, and for the seven zones. For each variable, the type of statistic (mean, proportion) and the base population (all women, currently married women) are given in Table A.1. For each variable, Table A.I presents the value of the statistic, R, its standard error, SE, the actual number of cases, N, the weighted number of cases, WN, the DEFT value, and the relative standard error, SE/R. In addition to these indicators, for the entire country ROH and the 95 percent confidence limits, R-2SD and R+2SD are presented. ROH is is a measure of homogeniety. A value of ROH closer to zero indicates more homogeniety in the cluster.
In general, the sampling errors for the country as a whole are small, which means that the SLDHS results are reliable. For example, for the variable children ever born, the overall average from the sample is 3.009 and its standard error is 0.030. Therefore, to obtain the 95 percent confidence limits~ one adds and subtracts twice the standard error to the sample estimate, i.e., 3.009 +-(2 * 0.030), which means that there is a high probability (95 percent) that the true average nnmher of children ever born for all Sri Lankan women falls within the interval of 2.949 to 3.069. This same type of calculation can be made for any other of the variables listed.
Sampling errors, on the other hand, can be evaluated statistically. The sample of women ~selected in the SLDHS is only one of many samples of the same size that could have been selected from the same population, using the same design. Each one of these samples would have yielded results somewhat different from the sample that was actually selected. The variability observed between all possible samples constitutes sampling error, which, although it is not known exactly, can be estimated from the survey results.
Sampling error is usually measured in terms of the "standard error" of a particular statistic (mean, percentage, etc.), which is the square root of the variance of the statistic across all possible samples of equal size and design. The standard error can be used to calculate confidence intervals within which one can be reasonably sure the true value of the variable for the whole population falls. For example, for any given statistic calculated from a sample survey, the value of that same statistic as measured in 95 percent of all possible samples of identical size and design will fall within a range of plus or minus two times the standard error of that statistic.
If simple random sampling had been used to select women for the SLDHS, it would have been possible to use straightforward formulas for calculating sampling errors. However, the SLDHS sample design depended on stratification, stages, and clusters and consequently, it was necessary to utilize more complex formulas. The computer package CLUSTERS was used to assist in computing the sampling errors with the proper statistical methodology.
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 one indicates that the sample design is as efficient as a simple random sample and a value greater than one indicates the increase in the sampling error due to the use of a more c0mplex and less statistically efficient design.
Sampling errors are presented in Table A.1 of the survey Final Report for 32 variables considered to be of major interest. Results are presented for the whole country, for urban and rural areas, for three age groups, and for the seven zones. For each variable, the type of statistic (mean, proportion) and the base population (all women, currently married women) are given in Table A.1. For each variable, Table A.I presents the value of the statistic, R, its standard error, SE, the actual number of cases, N, the weighted number of cases, WN, the DEFT value, and the relative standard error, SE/R. In addition to these indicators, for the entire country ROH and the 95 percent confidence limits, R-2SD and R+2SD are presented. ROH is is a measure of homogeniety. A value of ROH closer to zero indicates more homogeniety in the cluster.
In general, the sampling errors for the country as a whole are small, which means that the SLDHS results are reliable. For example, for the variable children ever born, the overall average from the sample is 3.009 and its standard error is 0.030. Therefore, to obtain the 95 percent confidence limits~ one adds and subtracts twice the standard error to the sample estimate, i.e., 3.009 +-(2 * 0.030), which means that there is a high probability (95 percent) that the true average nnmher of children ever born for all Sri Lankan women falls within the interval of 2.949 to 3.069. This same type of calculation can be made for any other of the variables listed.
Access policy
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
Access authority
| Name | Affiliation | URL | |
|---|---|---|---|
| MEASURE DHS | ICF International | archive@measuredhs.com | www.measuredhs.com |
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.
Metadata production
DDI Document ID
DDI_LKA_1987_DHS_v01_M
Producers
| Name | Abbreviation | Role |
|---|---|---|
| World Bank, Development Economics Data Group | DECDG | Generation of DDI documentation |
Date of Metadata Production
2012-05-23