SOME IMPROVED RATIO-TYPE ESTIMATORS OF FINITE POPULATION VARIANCE IN SAMPLE-SURVEYS

This paper proposes a class of ratio-type estimators of finite population variance and variance ratio when the population variance of an auxiliary character is known. Asymptotic expressions for bias and mean square error are derived and their MSE's are compared with the MSE of usual ratio estimator t1 proposed by Isaki (1983) of S2y, the population variance of study character y. The regions are obtained under which proposed estimator is superior to t1. When a prior knowledge of the value of coefficient of kurtosis, β2(y), of y is at hand, ratio type estimator, say t2, of S2y, is suggested. It is shown, under certain conditions, that t2 is more efficient than t1. Under some further knowledge another estimator of S2y, better than t1 and t2, is proposed. Finally, one more class of estimator is proposed and its properties are discussed. The discussions are also made in bivariate normal population. © 1990, Taylor & Francis Group, LLC. All rights reserved.