It is a statistical technique. Various business improvement processes, such as 6-sigma, use this technique to measure how well a process works and the impact of changes. "Simply stated, regression analysis is a statistical method that determines the extent to which a relationship exists between two variables." (Note: Some regression analysis techniques can assess the impact of more than one variable on another and test for non-linear relationships.)
The PMBOK, 5th edition, mentions it in section 126.96.36.199.
- Wikipedia article on regression analysis.
- "Estimating project costs with regression and risk analysis", by Pentico, David W. Project Management Journal. March 1985. Posted on PMI site.
- Regression Analysis on the Statgraphics site gives a short description of multiple kinds of regression statistics.