Determination of sample sizes for epidemiological surveys using cluster sampling technique.

Cluster sampling often provides a convenient and low cost device, in epidemiological surveys. The sample size needed under cluster sampling is generally larger than that in an individual based scheme due to the intra-class correlation existing in a cluster. This intra-class correlation coefficient is usually not known and some assumptions or estimates are essential. The strengths and weaknesses of cluster sampling over other sampling plans are presented and briefly discussed in this paper with particular reference to leprosy control programmes. One particular model of multistage cluster sampling technique is suggested in the evaluation of a District level programme, which includes determining the effectiveness of Multi-Drug Therapy, monitoring efficiency of paramedical workers and estimating the incidence of leprosy.