The Murthy (1957) estimator has been extensively studied by various
authors. The design based variance of the estimator has been studied by
the various survey statisticians. The modifications of the Murthy (1957)
estimator has been proposed by Shahbaz (2004) alongside the design based
study. The model based study of the estimator has been presented in this
monograph. We have also studied the stability of the variance estimator
of the modified Murthy (1957) estimator under the linear
super-population model. It has been observed that the anticipated
variance of the modified Murthy (1957) estimator achieves the
Godambe-Joshi (1965) lower bound and the variance estimator is stable.