A CLASS OF IPPS SAMPLING SCHEMES.

This paper introduces a general class of Inclusion Probability Proportional to Size (IPPS) sampling schemes for selecting two units from a finite population. All IPPS sampling schemes, identified as particular members of this class, possess some desirable properties with regard to the inclusion probabilities, and provide unbiased and non-negative variance estimators under Horvitz-Thomson (HT) model. [ABSTRACT FROM AUTHOR]