The sampling frame is a (physical) representation of all the elements in the population from which the sample in drawn.Although the sampling frame is useful in providing a listing of each element in the population, it may not always be a current, up-to-date document.When the sampling frame does not exactly match the population coverage error occurs.Screening the respondents with respect to important characteristics to ensure that meet the criteria for the target population.Adjusting the collected data by a weighting scheme to counterbalance the coverage error.