How is RAT-STATS used to determine the Full Sample size?
Once the mean and standard deviation of the overpayment amount in the Discovery Sample have been calculated, the Full Sample size can be determined. Select the “Sample Size Determination” tab on the main menu. Select “Variable Sample Size Determination,” “Unrestricted,” and “Using a Probe Sample.” RAT-STATS will ask for the following information: • probe sample format (e.g., text file, excel file, etc.); • universe size (i.e., the total number of sampling units from which the Discovery Sample was selected); • required confidence and precision levels; and • select the format of the data output (text file, printer, or screen). The results indicate the estimated number of units that should be sampled to achieve the specified confidence and precision levels. The number of sampling units to be selected for the Full Sample should correspond to the 90% confidence and 25% precision levels, as required by current CIAs. Note: Sample sizes vary according to the variability of the overpayments in
