As a high maturity (HM) lead appraiser, I spend a lot of time helping people understand how NOT to apply statistical concepts on their projects. That is, an appraisal finding is essentially saying, Here's where you're messing up a bit - stop doing that! Having led 37 +/- 2 HM appraisals, I have identified a set of recurring themes in HM appraisal findings. Note that most of these are not fatal falws, that is, the org may still get their desired HM rating. However, understanding, or better yet, avoiding these oft-recurring issues may help your projects achieve higher levels of performance - which is really what CMMI-based performance improvement is all about!