  The objective of this paper is to propose an unbiased ratio-type estimator
for finite population mean when the variables are negatively correlated.
Hartley and Ross[2] and Singh and Singh [6] estimators are identified as
particular cases of the proposed unbiased estimator. The variance expression of
the proposed estimator to the first degree of approximation has been obtained.
An empirical study is carried out to demonstrate the performance of the
proposed estimator over, Robson [5] estimator and Singh and Singh [6]
estimator.
