On Classes of Modified Ratio Type And Regression-Cum-Ratio Type Estimators in Sample Surveys Using Two Auxiliary Variables

In this paper generalized classes of modified ratio type and regression-cum-ratio type estimators of the finite population mean of the study variable are suggested in the presence of two auxiliary variables in simple random sampling without replacement when the population means of the auxiliary variables are known in advance. Some special cases of the generalized estimators are compared with respect to their biases and efficiencies both theoretically and with the help of some natural populations.