There are two types of appraisals supported by the CMMI Institute: an Evaluation Appraisal, designed to evaluate all or part of your processes to gauge compliance with the model, and the Benchmark Appraisal, designed toevaluate and convey Capability or Maturity Levels. In practice, we divide these into Gap Analyses, Evaluation Appraisals, and Benchmark Appraisals.
A Gap Analysis, formally the low end of an Evaluation Appraisal, is designed to gauge the state of an organization's processes or artifacts. It is normally conducted by one or two people, one of what is the Appraisal Leader. Two or more Gap Analyses may be necessary in an adoption effort.
The more robust type of Evaluation Appraisal is conducted by a team of people, and is designed to conduct interviews, present Findings, and go through many or most of the steps of a Benchmark Appraisal - expect that ratings may not be conferred.
A Benchmark Appraisal is designed to provide the Capability or Maturity Level(s) of a set of processes. A team of at least four Appraisal Team Members is required, one of whom may be the Appraisal Team Leader. The results of a Benchmark Appraisal are typically reported to the CMMI Institute for a final quality review.