the aim of sampling is to obtain fairly precise results about
population parameters of the study variable on the basis
of random samples. The simplest estimator of population
parameter is based on simple random sampling when there is
no additional information is available.
In sampling theory it is
usual to make use of information on auxiliary variables to
obtain more efficient estimators. Some of the estimation
procedures in sampling theory exploit the use of correlation
between the variables and for the purpose of enhancing the
precision of the estimators where the information on the
auxiliary variable is known.. It is well known that when the
auxiliary information is available, the ratio,
product and
regression estimators are widely utilized in many situations.
Theoretically, it has been established that,
in general, the
regression estimator is more efficient than the ratio and product
estimators except when
the regression line of the character
under study on the auxiliary character passes through the
neighbourhood of the origin. In this case the efficiency of the
estimators is almost equal