Chapter 8: Step 5: Identify Ground Rules and Assumptions

Cost estimates are typically based on limited information and therefore are dependent on several suppositions that make it possible to complete the estimate. These suppositions are called ground rules and assumptions. Ground rules and assumptions (GR&As) typically define the estimate’s scope and establish baseline conditions on which the estimate is based.

By reviewing the technical baseline and discussing the GR&As with customers early in the cost estimating process, analysts can flush out any potential misunderstandings. GR&As

• satisfy requirements for key program decision points,
  
• answer detailed and probing questions from oversight groups,
  
• help make the estimate complete and professional,
  
• present a convincing picture to people who might be skeptical,
  
• provide useful estimating data and techniques to other cost estimators,
  
• provide for reconstruction of the estimate when the original estimators are no longer available, and
  
• provide a basis for the cost estimate that documents areas of potential risk that can be identified and eventually treated.

Ground rules and assumptions are distinct even though they are often grouped together.