<prompt> Estimation of percentage of children immunized in community as per WHO is to be done by:Multistage random samplingCluster randomSystematic random samplingAll of the above  <response>: WHO recommends cluster random sampling CRS to estimate the percentage of children immunized in the community, paicularly in developing nations. Their recommended strategy is 30x7 sampling. Ref: Medical biostatistics, 1st edition pg: 201 