Afghanistan Mortality Survey 2010 - Measure DHS

A.3 STRUCTURE OF THE SAMPLE AND THE SAMPLING PROCEDUREThe sample for the AMS 2010 was a stratified sample selected in two stages from the samplingframe. Stratification was achieved by separating each domain into urban and rural areas. Because of thelow urban proportion for most of the provinces, the urban areas all together of each domain form a singlesampling stratum, which is the urban stratum of the domain. On the other hand, the rural area of eachdomain is further split into strata according to province, that is, the rural area of each province forms asampling stratum. In total, 34 sampling strata were created after excluding the rural areas of Kandahar,Hilmand and Zabul from the domain of the South. Among the 34 sampling strata, 3 of them are urbanstrata; the remaining 31 strata are rural strata which correspond to the total number of provinces with theirrural areas included in sample selection. Samples were selected independently in each sampling stratum,by a two-stage selection. Implicit stratification and proportional allocation has been achieved at each ofthe lower administrative levels within a sampling stratum, by sorting the sampling frame according toadministrative units at different levels within each stratum and by using a probability proportional to sizeselection at the first stage of sampling.The 24,000 sample households were equally allocated to each sample domain, that is, 8,000households per domain which is the minimum number of households needed in order to get an adequateprecision for the maternal mortality ratios (MMR) estimation at each domain. The 8,000 households werethen allocated to each sampling stratum within the survey domain. Ideally households should be allocatedto the sampling stratum proportionally to the stratum size, but this would result in a very small urbansample for the country as a whole because of the small proportion of the country that is urban. In orderthat the minimum requirement of sample size be guaranteed for both urban and rural areas, because urbanand rural areas are two different study domains, the urban area in each survey domain was oversampled.After fixing the urban sample size of each domain, the remaining sample was allocated to the rural strataof the domain with sample sizes proportional to their size. A fixed number of 32 households were selectedfrom each EA in the second stage; the household allocation for each sampling stratum was then convertedto the number of EAs. As a result of rounding, the total number of EAs selected was 751. Table A.3shows the sample distribution of households and EAs. The total number of households selected for theAMS 2010 was 24,032 of which 7,584 are in urban areas and 16,448 are in rural areas. Among the 751EAs selected, 237 are in urban areas and 514 in rural areas.In the first stage, 751 EAs were selected with probability proportional to the EA size and withindependent selection in each sampling stratum with the sample allocation as given in Table A.3. Beforefieldwork, a household listing operation was carried out in all of the selected EAs. The household listingoperation consists of visiting each of the 751 selected EAs; drawing a location map and a detailed sketchmap; and recording on the household listing forms all structures found in the EA, and all householdsresiding in the structure with the address and the name of the head of the households. The resulting list ofhouseholds served as the sampling frame for the selection of households at the second stage of sampling.The sample households for the AMS 2010 were selected randomly with equal probability from the newlycreated household listings for every cluster. Interviewers were asked to interview only the pre-selectedhouseholds; no replacement of non-respondent households was allowed in the field during surveyimplementation. This was aimed at preventing the introduction of any bias by interviewers should theyattempt to replace households which are easier to reach. Interviewers were trained to make every effort tointerview all pre-selected households thereby reducing the non-response bias to a minimum. Excelprograms were prepared to facilitate the household selection in the central office.148 | Appendix A