Cook’s Distance (Di) is used for assessing influence in regression models. The usual criterion is that a
point is influential if Di exceeds the median of the Fp,n-p
distribution, where p is the number of regression
parameters. The practice developed here at Massey Albany is to teach the guideline Di>0.7 for p=2, Di>
0.8 for p=3, Di> 0.85 for p>3, where n≥15. It is not known if this guideline is used elsewhere.
McDonald, B. (2002), A teaching note on Cook's distance - a guideline, Research Letters in the Information and Mathematical Sciences, 3, 122-128