Originally posted by Kevin Mader
RCW,
Dr. Juran noted that inspection was at best, 80% accurate. Others have guessed less, but that doesn't really matter. Think of it this was. One inspector is .8 in 1 chance likely to find a problem. The second inspector has the same chance. However, if you take .8 and multiply it by .8 (the second inspector), your outcome is .64. With the second inspector, your odds are reduced thus making 200% inspection 64% likely to find a defect.
Dr. Deming offered this in regards 200% inspection: Inspector 1 thinks inspector 2 will catch the defect while inspector 2 thinks inspector 1 will catch it. Net result: nobody inspecting.
I hope this helps.
Kevin