Potential gains from sample design using unit level cost information

In developing the sample design for a survey we usually attempt to produce a good design for the funds available. Information on costs can be used to develop sample designs that minimise the sampling variance of an estimator of total for fixed costs. Improvements in survey management systems mean that it is now possible to estimate the cost of including each unit in the sample. This paper develops relatively simple approaches to determine whether the potential gains arising from using this unit level cost information are likely to be of practical use. It is shown that the key factor is coefficient of variation of the costs relative to the coefficient of variation of the relative error on the estimated cost coefficients.