350 Quality Assurance
• To uncover the changes, the key question is, What has changed
in, on, around, or about the difference and when did the change
occur? A good guideline to develop changes is to:
− List all changes that occurred related to difference regardless
of date or their potential for cause
− Consider the categories of people, methods, materials,
machines, measurement, and Mother Nature (environment)
Once the IS/IS NOT analysis is nished, the team is ready to begin the
identication and/or the development of possible cause (change-how theo-
ries). At this stage, theories are
• Statements of ways that the changes may have created the trouble
• A limited form of brainstorming
• Simply a listing of possible causes not probable causes ...