Defining the Universe, the Sampling Unit, and the Sampling

8.4.3.2 - Defining the Universe, the Sampling Unit, and the Sampling Frame (Rev. 11962; Issued: 04-21-23; Effective: 05-22-23; Implementation: 05-22-23) The universe is the target population that contains all claims/claim lines potentially under review and is used to construct the sampling frame. The sampling frame lists all sampling units which may be selected by the statistical sampling software, and further refines the review criteria from the claims/claim lines listed in the universe. The sampling unit may be the claim line, or may be a higher-level unit such as: 1. The claim/claim number, or 2. A cluster of claims/claim lines associated with a patient, or 3. A cluster of claims/claim lines associated with a treatment “day,” or 4. Any other sampling unit appropriate for the issue under review. The auditor may refine the selection criteria during the construction of the sampling frame, for example: 1. Excluding claims/claim lines that have been subject to a prior review, or 2. Excluding claims/claim lines for which there was no payment, or 3. Excluding claims/claim lines which cannot be assigned to a sampling unit due to missing information. The extrapolation estimate of total overpayments is an estimate of total overpayment for sampling units in the sampling frame. All information needed to recreate the sampling frame and sample shall be included in the case documentation. Other approaches to constructing the universe and sampling frame are possible depending on the specific circumstances. One possibility is that the sampling frame may be created first (for example, a list of beneficiaries) and then the universe corresponding to the sampling frame may be constructed by querying claims history for the matching claims. Regardless of the process that is followed, the documentation in the case file must include a list of all sampling units in the sampling frame, all the universe elements that are incorporated into those sampling units, and the elements in the universe. It must be possible to assemble the sampling units from the universe during the replication process.