Hartley-Ross type unbiased estimators of population mean using two auxiliary variables

In survey sampling, it is a well-established phenomenon that the eciency of estimators increases with proper information on auxiliary variable(s). Keeping this fact in mind, the information on two auxiliary variables was utilized to propose a family of Hartley-Ross type unbiased estimators for estimating population mean under simple random sampling without replacement. Minimum variance of the new estimators was derived up to the rst degree of approximation. Three real datasets were used to verify the ecient performance of the new family in comparison to the usual unbiased, Hartley and Ross, and other competing estimators.