คำศัพท์คณิตศาสตร์
The use of auxiliary information improves the efficiency of estimators. Cochran (1940) used auxiliary information at the estimation stage and envisaged the ratio estimation method. This method provides a ratio estimator which assumes that the population mean of the auxiliary variate is known. The ratio estimator performs well when a study and auxiliary variate are positively correlated. When these variates are negatively correlated, Robson’s (1957) product method, which was independently given by Murthy (1964), is used. Searls (1964) utilized the coefficient of variation of an auxiliary variate to estimate the population mean of a study variate. Based on the work of Searls (1964), Sisodia and Dwivedi (1981) used a coefficient of variation of an auxiliary variate. Singh, et al. (2004) proposed ratio and product type estimators using the coefficient of kurtosis of an auxiliary variate, whereas Upadhyaya and Singh (1999) utilized both the