The physical process of selection involves the proper use of a table of random numbers. The suggestion to use systematic selection is made whether the process involves sampling in each stratum of a frame or whether the whole frame is used directly. The greater administrative and technical ease in verification and audit of the sampling process is the basis for the suggestion to use systematic sampling. A record should be kept of the manner of determining the sampling interval and the random start in case it becomes necessary to audit the process. Estimation is the process of determining the amount of overpayment by using the readjudicated result for each sampling unit in the sample and knowledge of the sampling procedure.
Sample design comprises both sample selection and estimation.
The sample results may be used to estimate the degree of variability that would be observable among all possible samples, using the same sampling and estimation methods. The estimate of sampling variability is necessary in determining the confidence limits of that mount of overpayment. There may be a variety of factors affecting the validity of the estimates of overpayment. Collectively, these factors are describable as nonsampling errors. Nonsampling errors may arise as a result of differences between the universe and the frame.