LKA_2006_DHS_v01_M
Demographic and Health Survey 2006-2007
Name | Country code |
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Sri Lanka | LKA |
Demographic and Health Survey (standard) - DHS IV
Sri Lanka has conducted several surveys related to fertility, family planning, and reproductive health. The first of this type was the World Fertility Survey conducted in 1975. The World Bank Fertility Survey (1979), the Contraceptive Prevalence Survey (1980), and the Sri Lanka Contraceptive Prevalence Survey (1985) all followed after that first nationwide fertility survey. Then a series of Demographic and Health Surveys (DHS) was carried out in 1987, 1993, and 2000. DHS is an improved version of the earlier fertility surveys with additional modules to collect information on maternal and child health, nutrition, reproductive health and child survival, and other topics. The Sri Lanka Demographic and Health Survey (SLDHS) of 2006-07 is a continuation of the DHS series.
Sample survey data
The Sri Lanka Demographic and Health Survey 2006-07 covers the following topics:
A nationally representative sample of 21,600 housing units was selected for the survey and 19,872 households were enumerated to give district level estimates (excluding Northern Province).
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 wereall ever-married women aged 15-49 years who slept in the household the previous night and about their children below five years at the time of the survey.
Name | Affiliation |
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Department of Census and Statistics (DCS) | |
Health Sector Development Project (HSDP) | Ministry of Healthcare and Nutrition |
Name | Role |
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Macro International Inc. | Technical assistance |
Name | Role |
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The World Bank | Funding |
Name | Affiliation | Role |
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United Nations Children's Fund | UNICEF | Provider of technical material |
The 2006-07 SLDHS sample was designed to produce key indicators for the country as a whole, and for sectors (urban, rural, and estate) and districts. All 25 districts of Sri Lanka were included at the design stage. The final sample has only 20 districts, however, after dropping the 5 districts of the Northern Province (Jaffna, Kilinochchi, Mannar, Vavuniya, and Mullativu), due to the security situation there. The districts in the other 8 provinces are given below:
The SLDHS used a stratified two-stage cluster sample design. The sample was spread geographically more or less proportionally to the population. The first stage involved selecting 2,500 enumeration areas (clusters) from the list of about 100,000 enumeration areas (EAs) formed in the 2001 Population Census. The objectives of the sampling design were to provide reasonably accurate estimates at three levels-national, sector (urban, rural, estate), and district-and to provide estimates for tsunami-affected areas as well. In order to provide reliable estimates for these levels, some districts were oversampled. Therefore, the final sample is not self-weighting, and weighting factors were used to make the sample be proportional to the population. Weighted data are used throughout the report, unless otherwise noted.
An enumeration area (EA) is a subdivision of a Grama Niladari area, which consists of about 80 housing units in urban areas and about 65 units in rural or estate areas. The criterion used in creating an EA is that one enumerator can visit all the units in the area within six hours to take a count of all the units and the people residing therein. A household list of each EA (including information on housing units) along with a map is available at DCS to be used as a frame for selection of samples for surveys.
The second stage of selection involved the systematic sampling of 10 households listed in each enumeration area. Thus, 2,500 clusters were selected initially: 469 urban, 1,831 rural and 200 estate. In the end, information was collected from 2,106 clusters. The remaining 394 clusters were not enumerated (340 clusters from Northern Province due to unsettled conditions prevailing in the province at the time of the survey, and 54 clusters from other areas). The reasons for elimination were: temporary tsunami camps (5 clusters), unstable security conditions (45), and landslides that prevented access to the clusters (4).
For the final sample (which excluded the Northern Province), 21,060 housing units were selected, and 19,862 households were interviewed. All ever-married women age 15-49 years living in these households were eligible to be interviewed. Eligible respondents were either usual residents of the households or visitors present in the household on the night before the interview date.
There are certain limitations in comparing the findings of this survey with those from the 2000 SLDHS. The earlier survey did not include the Eastern Province, whereas the 2006-07 SLDHS did include it. However, neither the 2000 DHS nor the 2006-07 DHS covered the Northern Province. Thus when comparisons are made to the 2000 SLDHS, the data for the current survey are shown with the Eastern Province also excluded. As a result, the statistics for 2006-07 in such tables may differ slightly from tables presenting the 2006-07 SLDHS data only.
A total of 21,600 housing units were selected for the sample, from which 21,357 households were located, and 20,317 were occupied at the time of the survey. Of those existing households, 19,862 were successfully interviewed, yielding a household response rate of 98 percent. The household response rate is slightly higher in the rural sector than in the urban and estate sectors.
Within the households interviewed, a total of 15,068 eligible women (ever-married women age 15-49) were identified, of whom 14,692 were successfully interviewed, yielding a response rate of 98 percent. The eligible women's response rate is also slightly higher in rural areas than urban and estate areas.
The principal reason for non-response among eligible women was the failure to meet them at home despite repeated visits to the households. There were very few partially completed cases, and refusals were very minimal.
The 2006-07 SLDHS questionnaire, which was used to collect information from households and eligible women through personal interviews, contained the topics mentioned below. An effort was made to incorporate globally recommended standard questions as much as possible. Model questionnaires developed by MEASURE DHS were used with some modifications to match the local situation. Additional questions were also included to satisfy the needs of the health sector and also to provide data for the compilation of UNICEF's World Fit for Children and Millennium Development Goals (MDG) indicators.
The questionnaire had two main sections, namely, a household section and a section on women and children.
a) The first section served two purposes. One was to list all the usual members and visitors in the selected household together with some basic information about them-such as age, education, marital status, nature of residence, and relationship to the head of household. This information was used to identify eligible women and children for the main interview and also to provide denominators for analysis of some of the household characteristics. The second purpose was to collect information on characteristics of the household's dwelling. Information of this type included source of drinking water, toilet facilities, construction materials of the home, land tenure, garbage disposal, ownership of livestock and various durable goods, use of iodized salt, and use of mosquito nets (including treated nets). There were also questions about several non-communicable diseases, adequacy of basic requirements for school-going children, and information about orphanhood. Children under five and women 15-49 were eligible to be weighed and measured and have their haemoglobin level measured.
b) The second section, the questionnaire for ever-married women, covered the following topics:
Respondents were also asked an extensive series of questions about their children below 5 years at the time of the survey. Topics covered were vaccinations, childhood illnesses, nutrition status, and breastfeeding. In addition, a calendar of events was used to record information related to respondent's marriage, pregnancies and births, and contraceptive use in a specially designed chart for a five-year period prior to the survey.
The complete questionnaire was pre-tested by a team of experienced staff to test the feasibility, sequence, skipping, and timing before it was finalized. The questionnaire was prepared in Sinhala and Tamil; an English version was used occasionally for a few interviews.
Start | End |
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2006-09 | 2007-10 |
Name |
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Department of Census and Statistics |
Senior staff of DCS were appointed as district coordinators. The overall responsibility of the coordinators was to ensure the smooth implementation and good quality of fieldwork. Their tasks included checking completed questionnaires for quality and managing logistics, such as transport and accommodations. A survey expert from Macro also made two visits in 2006 (in August-September and late October-early November) to observe field work and review completed questionnaires and give feedback to interviewers.
A new feature was added to this round of the SLDHS to improve the quality of fieldwork. A special set of tables was generated, which were used to measure the quality of fieldwork. If any deviations from the expected targets were found, the teams were informed and instructed on remedial actions.
TRAINING
Altogether SLDHS used 222 field workers. Although the majority consisted of DCS staff who were experienced in conducting surveys, about 80 female enumerators were hired to collect information for Tamil-speaking households. In addition, 12 office staff worked in the DHS unit to provide assistance in coordination of survey activities. Many of the DCS staff had participated in either the SLDHS pre-test or a prior survey of this nature.
DCS organized a three-week training program, offered separately for its Sinhala-speaking and Tamil-speaking staff. The training in Sinhala was carried out by senior staff of the DCS and experts from the Ministry of Healthcare and Nutrition, the Family Planning Association, and the Water Board. A consultant was hired to conduct the training of Tamil speakers.
Besides giving a complete description of each question and its purpose, the training included mock interviews, special lectures giving background information, and field trials. District coordinators for the fieldwork received a few days of training about their special duties and responsibilities in addition to the enumerator training.
Both the training and the fieldwork had two tracks defined by language-one for Sinhala speakers and the other for Tamil speakers. There were three trainings of Sinhala-speaking field staff. The first was in June 2006. The second training (in June 2007) was needed to replace enumerators who had dropped out. The third training took place in September 2007 in the Eastern Province, where local Sinhala-speaking women were hired as interviewers because enumerators from other parts of the country were reluctant to go there due to the security situation.
Two trainings of Tamil-speaking field staff took place in late March 2007 and mid-July 2007. The second training was necessary to replenish the enumerator pool and to be able to collect data in the Eastern Province. The delay in conducting the training, and therefore also the fieldwork, for predominantly Tamil-speaking areas was due to recruitment issues. The ongoing unstable situation in the eastern part of the country affected the recruitment of Tamil field enumerators among DCS staff. Instead, DCS recruited Tamil field enumerators locally from the districts in which they reside to minimize dropouts.
Officers of the Medical Research Institute of Sri Lanka trained measurers and their assistants in obtaining height and weight measurements and medical officers in conducting haemoglobin testing.
The training incorporated field practice sessions for these personnel as well. The measurers were trained before each enumerator training.
FIELDWORK
Fieldwork in Sinhala-speaking communities was carried out in three phases. The first was from August 2006 to September 2007 in mainly Sinhala-speaking areas; the second was from February to September 2007 in districts where both Sinhala and Tamil are spoken; and the third was in September and October 2007 in Sinhala areas of Eastern Province.
Fieldwork in Tamil-speaking communities occurred from May to July 2007 and then from August through October 2007. In the sample there were about 200 blocks with a mixture of communities speaking Sinhala or Tamil, for which both Sinhala and Tamil-speaking teams were employed to do the survey. These interviews were concentrated in the second and third phases of the Sinhala fieldwork.
The very large sample meant that data collection spanned a longer period of time than is typically needed for this type of survey. Three-fourths of all the eligible respondents were interviewed in Sinhala by early April 2007. The remainder of the interviews took place over the next seven months. With a smaller sample size it is usually possible to complete data collection between the monsoon seasons in Sri Lanka. Fieldwork for the 2006-07 SLDHS had to be suspended for about six weeks in November and December 2006 due to rain and floods.
A total of 24 teams (15 Sinhala teams and 9 Tamil teams) were formed for data collection. Each team comprised one female supervisor, four female interviewers, one field editor, a measurer (for height and weight and GPS measurements), and a field assistant. Senior staff of DCS were appointed as district coordinators. The overall responsibility of the coordinators was to ensure the smooth implementation and good quality of fieldwork. Their tasks included checking completed questionnaires for quality and managing logistics, such as transport and accommodations. A survey expert from Macro also made two visits in 2006 (in August-September and late October-early November) to observe field work and review completed questionnaires and give feedback to interviewers.
A new feature was added to this round of the SLDHS to improve the quality of fieldwork. A special set of tables was generated, which were used to measure the quality of fieldwork. If any deviations from the expected targets were found, the teams were informed and instructed on remedial actions.
Haemoglobin tests for anaemia were to be carried out for mothers and their children under five at the time of the interview. However, suitable medical officers and equipment were unavailable until April 2007. In Tamil-speaking areas in the last few months of data collection, medical officers were sent with the survey teams to collect haemoglobin information, so there was no delay. Testing was done at the time of the interview in the three districts of the Eastern Province and in three 'mixed' districts (both Tamil- and Sinhala-speaking). In another seven mixed districts, the testing was done at the time of interview for Tamil-speaking households only. The interviews and testing for Sinhalaspeaking households in these districts were done at different times. Testing was also done in a separate visit to households for the other seven Sinhala-speaking districts. Thus there was a time gap of 5 to 14 months between the time of household interviews done in 2006 to the time when haemoglobin levels were taken; and 2 to 9 months for interviews from January through May 2007. When a separate visit was required to do haemoglobin testing, some women and children could not be matched to the original interview information or were not found. Because of these various difficulties in tabulating and interpreting the data, it was decided to omit the results from the haemoglobin testing from this report until the data could be properly analyzed.
Processing SLDHS data began a few weeks after the fieldwork commenced. Completed questionnaires were returned periodically from the field to the Data Processing Division in Colombo, where they were coded manually by staff specially trained for this task. Processing the data concurrently with fieldwork was a distinct advantage for data quality, since the survey unit was able to advise field teams of errors detected during data entry.
A group of experienced data entry persons at DCS did data entry. Two consultants from Macro assisted the Data Processing Division and DHS Unit staff by giving necessary guidance for manual coding and editing, data entry, verification, online editing, and machine editing. Data were entered using the CSPro computer package. All data were entered twice (100 percent verification). Two DCS staff members who were specially trained for this purpose did machine editing. Data entry was completed in December 2007. DCS completed machine editing of the data file in mid-January 2008. A Macro Data Processing Specialist visited Colombo in February 2008 to work with DCS staff to produce the final data file and run preliminary tables.
The estimates from a sample survey are affected by two types of errors: nonsampling errors and sampling errors. Nonsampling errors are the results of mistakes made in implementing data collection and data processing, such as failure to locate and interview the correct household, misunderstanding of the questions on the part of either the interviewer or the respondent, and data entry errors. Although numerous efforts were made during the implementation of the 2006-07 Sri Lanka Demographic and Health Survey (SLDHS) to minimize this type of error, nonsampling errors are impossible to avoid and difficult to evaluate statistically.
Sampling errors, on the other hand, can be evaluated statistically. The sample of respondents selected in the 2006-07 SLDHS 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 2006-07 SLDHS 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 the 2006-07 SLDHS is a Macro SAS procedure. 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 2006-07 SLDHS, there were 2,106 non-empty clusters. Hence, 2,106 replications were created.
In addition to the standard error, the procedure 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. The procedure also computes the relative error and confidence limits for the estimates.
Sampling errors for the 2006-07 SLDHS are calculated for selected variables considered to be of primary interest for the women's survey and for the men's surveys, respectively. The results are presented in an appendix of the Final Report for the country as a whole, for urban, rural and estate areas, and for each of the 20 districts of 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.25 present the value of the statistic (R), its standard error (SE), the number of unweighted (N-UNWE) and weighted (N-WEIG) 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 the case of the total fertility rate, the number of unweighted cases is not relevant, as there is no known unweighted value for woman-years of exposure to child-bearing.
The confidence interval (e.g., as calculated for children ever born) can be interpreted as follows: the overall average from the national sample is 1.434 and its standard error is 0.026. Therefore, to obtain the 95 percent confidence limits, one adds and subtracts twice the standard error to the sample estimate, i.e., 1.434±2×0.026. There is a high probability (95 percent) that the true average number of children ever born to all women is between 1.381 and 1.487.
For the total sample, the value of the DEFT, averaged over all variables, is 1.104. This means that, due to multi-stage clustering of the sample, the average standard error is increased by a factor of 1.104 over that in an equivalent simple random sample.
Name | URL | |
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National Data Archive | http://statistics.sltidc.lk/index.php/policies-and-procedures | data.requests@statistics.gov.lk |
Department of Census and Statistics (DCS) and Ministry of Healthcare and Nutrition (MOH). 2009. Sri Lanka Demographic and Health Survey 2006-07. Colombo, Sri Lanka: DCS and MOH.
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.
Name | URL | |
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Department of Census and Statistics | information@statistics.gov.lk | www.statistics.gov.lk |
General Inquiries | info@measuredhs.com | www.measuredhs.com |
Data and Data Related Resources | archive@measuredhs.com | www.measuredhs.com |
DDI_LKA_2006_DHS_v01_M_WBDG
Name | Role |
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World Bank, Development Economics Data Group | Generation of DDI documentation |
2012-05-23
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