Sampling Procedure
Sample Design
Outline of sample design: A stratified multi-stage design has been adopted for the 59th round survey. The first stage unit (FSU) is the census village in the rural sector and UFS block in the urban sector. The ultimate stage units (USUs) will be households in both the sectors. Hamlet-group / sub-block will constitute the intermediate stage if these are formed in the selected area.
Sampling Frame for First Stage Units: For rural areas, the list of villages (panchayat wards for Kerala) as per Population Census 1991 and for urban areas the latest UFS frame, will be used as sampling frame. For stratification of towns by size class, provisional population of towns as per Census 2001 will be used.
Stratification
Rural sector: Two special strata will be formed at the State/ UT level, viz.
- Stratum 1: all FSUs with population between 0 to 50 and
- Stratum 2: FSUs with population more than 15,000.
Special stratum 1 will be formed if at least 50 such FSU's are found in a State/UT. Similarly, special stratum 2 will be formed if at least 4 such FSUs are found in a State/UT. Otherwise, such FSUs will be merged with the general strata.
From FSUs other than those covered under special strata 1 & 2, general strata will be formed and its numbering will start from 3. Each district of a State/UT will be normally treated as a separate stratum. However, if the census rural population of the district is greater than or equal to 2 million as per population census 1991 or 2.5 million as per population census 2001, the district will be split into two or more strata, by grouping contiguous tehsils to form strata. However, in Gujarat, some districts are not wholly included in an NSS region. In such cases, the part of the district falling in an NSS region will constitute a separate stratum.
Urban sector: In the urban sector, strata will be formed within each NSS region on the basis of size class of towns as per Population Census 2001. The stratum numbers and their composition (within each region) are given below.
- stratum 1: all towns with population less than 50,000
- stratum 2: all towns with population 50,000 or more but less than 2 lakhs
- stratum 3: all towns with population 2 lakhs or more but less than 10 lakhs
- stratum 4, 5, 6, ...: each city with population 10 lakhs or more
The stratum numbers will remain as above even if, in some regions, some of the strata are not formed.
Total sample size (FSUs): 10736 FSUs have been allocated at all-India level on the basis of investigator strength in different States/UTs for central sample and 11624 for state sample.
Allocation of total sample to States and UTs: The total number of sample FSUs is allocated to the States and UTs in proportion to provisional population as per Census 2001 subject to the availability of investigators ensuring more or less uniform work-load.
Allocation of State/UT level sample to rural and urban sectors: State/UT level sample is allocated between two sectors in proportion to provisional population as per Census 2001 with 1.5 weightage to urban sector subject to the restriction that urban sample size for bigger states like Maharashtra, Tamil Nadu etc. should not exceed the rural sample size. Earlier practice of giving double weightage to urban sector has been modified considering the fact that two main topics (sch. 18.1 and sch 33) are rural based and there has been considerable growth in urban population. More samples have been allocated to rural sector of Meghalaya state sample at the request of the DES, Meghalaya.
The sample sizes by sector and State/UT are given in Table 1 at the end of this Chapter.
Allocation to strata: Within each sector of a State/UT, the respective sample size will be allocated to the different strata in proportion to the stratum population as per census 2001. Allocations at stratum level will be adjusted to a multiple of 2 with a minimum sample size of 2. However, attempt will be made to allocate a multiple of 4 FSUs to a stratum as far as possible.
Selection of FSUs: FSUs will be selected with Probability Proportional to Size with replacement (PPSWR), size being the population as per population census 1991 in all the strata for rural sector except for stratum 1. In stratum 1 of rural sector and in all the strata of urban sector, selection will be done using Simple Random Sampling without replacement (SRSWOR). Samples will be drawn in the form of two independent sub-samples.
Note: Detail sampling procedure is provided as external resource.