Adaptive Cluster Double Sampling

ACS introduced by Thompson (1990) has been found appropriate for sampling of rare and clustered populations. But it suffers from drawback of losing control of the final sample size. There have been several suggestions for limiting this final sample size of adaptive cluster samples. In this design, traveling costs are increased because the second phase sample is selected after the first phase sample is completed. In the second phase of the sampling design, the sampler cannot allocate the subsample near the places of interest. The proposed unbiased estimators of the population mean do not take the advantage of the relation between the variable of interest and the auxiliary variable.