Sri Lanka - Demographic and Health Survey - 2000

Sample Design
A muti-stage strtified probability sample representative of the surveyed area was used. The primary stratification was also the same as that used in the previous Demographic and Health Survey conducted in 1993. The country has been stratified into the nine zones on the basis of socio-economic and ecological criteria. As in the previous Demographic and Health Survey, this was also confined to the same seven zones, exluding the zone 8 ( Estern province ) and zone 9 ( Nothern province) due to the unsettled condition prevailed in these zones. The field operation in Nothern and Eastern provinces was also conducted at a latter date with the assistance of the District Adminstration and with the financial assistance from the UNICEF. data was collected from a sample of 1000 households from each of the two zones using a different sampling procedure. The data collected from these zones was processed seperately.

The seven zones that were included in the survey are :
Zone 1 : Colombo Metropolitan area consisting some urban areas in Colombo and Gampaha Districts.
Zone 2 : Colombo Feeder areas
Zone 3 : South Western Cosatal Low Lands
Zone 4 : Lower South Central Hill Country excluding Districts with a concentration of estates.
Zone 5 : South Central Hill country with a concentration of estates.
Zone 6 : Irrigated Dry Zone with major or minor irrigation schemes.
Zone 7 : Rain fed Dry Zones
The zones that were not included in the survey are :
Zone 8 : Eastern coastal belt ( Eastern Province )

Sample units
Primary Sampling Units (PSUs) are Wards in urban areas, Grama Niladhari (GN) divisions in rural areas and Individual Estates in the estate sector.
In urban areas Secondary Sampling Units (SSUs) were generally two census blocks per ward. In rural areas, generally one single village per GN division was selected as SSU. Therefore it can be said that in rural areas, villages form the effective PSUs. That means the outcome of the sample selection would have been particularly the same, had we selected villages directly. Housing units are the third stage Sampling Units (TSUs) in all the sectors.
Most of the estates are very small in size in terms of housing units. Therefore in the estate sector, SSUs are one or part or group of estates, depending on the size of the estates. To avoid the need to group the estates in the whole frame special procedure was applied to select estates depending on the relative size of the estate compared to nearby estate.

Sampling frame
Each zone was further stratified into three strata: urban, rural and estate sectors. Within each stratum, sampling areas were arranged acccording to the administrative and geographical locations. That is, a specially prepared list consisting of Wards, Grama Niladhari divisions and Estates, organized by zone, scetor and within sector geographically was used as the frame for one selection of PSUs. This organization provided a better basis for stratification as it is arranged on a geograhical basis. The list of census blocks prepared during the 1981 Census of Population and Housing was used as the frame for selection of SSUs in the urban sector. List of villages / estate of the selected PSU in the rural / estate sector were used as the frame for the selection of SSUs. The pre-listing forms prepared for the 1981 Census of Population and Housing were used as the frame for the selection of housing units, the Third Sampling Units (TSUs) in all the sectors.

Sample selection
In urban areas with wards as PSU's, generally two census blocks were selected per ward as SSUs with Probability Proportional to Size (PPS). The number of housing units were taken as the measure of size. The main exception to the above pattern was in zone 1. In Colombo areas there is little advantage in clustering sample block into wards, while in other urban centers such clustering has the major effect of reducing the number of different urban centers coming into the sample. Therefore, in Colombo urban areas a sample of blocks as PSU's were selected directly. This option has been followed for Colombo metropolitan area as well as other urban areas o Zone 1 in Colombo District. In rural areas, GN divisions as PSUs were selected with PPS. From the selected PSU, depending on the size of the villages, one or part or group of villages were selected with PPS. In all sectors, housing unit as the Third stage Sampling Units (TSUs ) were selected systematically from the pre-listing forms of selected census blocks. The survey covered private households in the selected areas. Population in institutions and institutional households were excluded.

Sample Size
The target sample size in terms of completed insterviews with eligible respondent was 7500. In order to achieve this sample size 258 PSUs, 703 SSUs and 8636 housing units as TSUs were selected from all sectors. Since there was no further sampling all the eligible respondents found in the selected housing units were included in the survey. Eligible respondents were defined as ever-married women in the age group 15-49 years who slept in the household the previous night. All children in the age group 3-59 months of all eligible respondents were taken for anthropometric measurements of height and weight. The sample was designed to provide independent estimates for seven zones in the country.


Household response rate was 96.3

Eligible women response rate was 96.6


Sample weights by zone.

Household and individual weights by zone.

Strata
Household Individual
Zone No Description weight weight

Zone 1 23 Colombo urban 0.943880 0.973800
13 Gampaha urban 0.889735 0.917709

Zone 2 20 urban 1.088290 1.547613
rural 1.639377 1.578678

Zone 3 30 Urban 1.609445 1.226201
Rural 1.136887 1.211052
Estate 1.233418 1.235958

Zone 4 40 Urban 2.085573 1.847192
Rural 1.795777 1.795150
Estate 1.803179 1.766880

Zone 5 51 Urban 1.680248 1.654108
Rural 1.653090 1.653516

52 Estate 0.654436 0.603671

Zone 6 61 Urban 0.212992 0.160635
Rural 0.157921 0.160885

62 Urban 0.589298 0.544230
Rural 0.556295 0.568745

Zone 7 71 Urban 0.148377 0.160139
Rural 0.158070 0.157002

72 Urban 0.508638 0.961175
Rural 1.138574 0.947419
Estate 0.921060 0.997155