Adaptive sampling design
The sampling design in which the method for selecting the sampling Units on which to make observations might rely on the observed values of the variable of interest. In a survey for estimating the plenty of a natural resource, for instance, the additional sites (the sampling units in this case) in the vicinity of high observed abundance may be added to the sample during the survey. The major aim in such a design is to attain the gains in precision or efficiency compared to the conventional designs of equivalent to the sample size by taking advantage of the observed characteristics of the particular population. For this type of sampling design the probability of the given sample of units is conditioned on the set of values of the variable of interest in the population