Abstract
Inverse sampling is an adaptive method whereby it is the sample size that is adaptive. On the basis of a new proof, Murthy’s estimator can now be applied with or without adaptive cluster sampling to inverse sampling to provide unbiased estimators of the mean and variance of the mean estimator. A number of sequential plans along with parameter estimates are considered including a general inverse sampling design, multiple inverse sampling when subpopulation sizes are known, quota sampling, multiple inverse sampling, and truncated multiple inverse sampling.