CMS Pub. 100-08, ch. 8, § 8.4.1.3

The major steps in conducting statistical sampling are --

(1) Identifying the provider/supplier;

(2) Identifying the period to be reviewed;

(3) Defining the universe (target population) and the sampling unit, and constructing

the sampling frame;

(4) Assessing the distribution of the paid amounts in the sampling frame to determine

the sampling design; it is very likely that the distribution of the overpayments will not

be normal. However, there are many sampling methodologies (for example, use of

the Central Limit Theorem) that may be used to accommodate non-normal

distributions. The statistician should state the assumptions being made about the

distribution and explain the sampling methodology selected as a result of that

distribution.

(5) Performing the appropriate assessment(s) to determine whether the sample size is

appropriate for the statistical analyses used, and identifying, relative to the sample

size used, the corresponding confidence interval;

(6) Designing the sampling plan and selecting the sample from the sampling frame;

(7) Examining each of the sampling units and determining if there was an

overpayment or an underpayment; and

(8) Estimating the overpayment. When an overpayment has been determined to exist,

the contractor shall follow applicable instructions for notification and collection of

the overpayment, unless otherwise directed by CMS.

For each step, the contractor shall provide complete and clear documentation sufficient to

explain the action(s) taken in the step and to replicate, if needed, the statistical sampling.