I’m a big follower of SEI’s Maturity Reports, but I'm confused about the phrase "Based on the total number of employees within the area of the organization that was appraised”. Does this refer to the Organization Unit, or the Organization within which the Organizational Unit operates?
The concept of "Organizational Unit" exists within the Standard CMMI Appraisal Method for Process Improvement or "SCAMPI," the appraisal methodology used to appraise an organization. The "OU" represents the organizational scope of the appraisal itself, not the entire organization.
An OU could be a geographical location ("everyone in Toledo"), a functional organization ("Software development"), a management tree ("everyone reporting to Bill") or some other segmentation.
The OU must be credible and verifiable by the Lead Appraiser. So something like "every project with less than two people" with only one project in the scope would NOT be credible! Don't laugh, there is a famous example of one company, outside of NA, that did this.
Appraisals are conducted against the "OU", so it is technically only the "OU" that is awarded a maturity or capability level, and hence is the foundation of the data that is published by the SEI.
So therefore, the data in the report comes out of the SCAMPI results, which report the size of the OU, not the overall oganization.