Improved and Robust Estimators for Finite Population Variance Using Linear Combination of Probability Weighted Moment and Quartiles as Auxiliary Information

By adapting the scheme of modification technique, we have developed some new ratio type variance estimators to estimate the finite population variance for skewed populations under survey. We have also derived the functions of efficiency to intensify the quality of efficacy of newly developed estimators. The bias and mean square error of present and newly developed estimators has been worked out through numerical problem to determine the improvement of newly developed estimators over present estimators.