Ratio, regression, product and difference estimators take advantage of auxiliary information at the estimation stage. However, when the population information is not known then double sampling method becomes necessary for estimation. [1] is of the opinion that estimation of required parameters can efficiently be done with ratio and regression methods of estimation with two-phase sampling or double sampling method. Double sampling for ratio estimation becomes necessary over double sampling for regression estimation if the data under consideration are well fitted by a straight line through the origin [2]. Among the authors who have recently contributed to the use of auxiliary variable(s) to establish various estimators for the population parameters are [3-5]. However, in both cases of ratio and regression estimations or the use of double sampling in ratio and regression estimations, there must exists positive correlation between the auxiliary variable x and study variable y. This article, empirically, investigates to ascertain the importance of correlation level in the use of auxiliary variable in estimating the population parameter using double sampling for regression estimation method.