WHO recommended Sampling method for Immunisation coverage evaluation
Simple random sampling
Cluster random sampling
Stratified random sampling
Convenience sampling
Cluster random sampling (CRS) Applicable when units of population are natural groups or clusters. Use of CRS in India: Evaluation of immunization coverage. WHO technique used in CRS: 30 x 7 technique (total = 210 children) 30 clusters, each containing 7 children who are 12 - 23 months age and are completely immunized for primary immunization (till Measles vaccine). Accuracy: Low error rate of only +- 5%. Limitation: Clusters cannot be compared with each other.
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