IBBS Field operations and monitoring manual English

Integrated Behavioral and Biological SurveillanceField Operations and Monitoring Manual4.4 Multistage Cluster Sampling Once the sampling frame has been developed,a sample of sites can be chosen either withMultistage cluster sampling is an appropriateprobability proportional to size (PPS) or withtechnique that can be used for HRGs which areequal probability. PPS selection should be usedassociated with various sites in a fixed manner.when establishments vary significantly in termsFor example, in case of street based FSWs, theof numbers of sex workers associated withfollowing procedure can be adopted:them (e.g., when there are larger sites with 3-5The first step involves development of thetimes as many sex workers as smallersampling frame. As part of the sampling frameestablishments) and when it is possible todevelopment, it is useful to list all the sitesobtain measures of size prior to samplewhere street-based FSWs can be located, andselection. Where the numbers of sex workersto gather information on the number of sexassociated with establishments are roughlyworkers associated with each site. Thiscomparable (i.e., vary in size by a factor of lessinformation is useful for 1) selecting clustersthan three), sampling with equal probabilitywith probability-proportional-to-size (PPS)will suffice.should this option be chosen, 2) determiningthe appropriate number of sex workers to beFinally, a list of sites along with number of FSWsampled from each cluster, and 3) determiningto be selected from each site is provided to thehow many sample sites must be chosen.survey team, for recruitment into the study.22