This might be what you're saying, and it's been a long time since I read Rogers' original work, but IIRC Rogers was following the standard deviations of the nor

This might be what you're saying, and it's been a long time since I read Rogers' original work, but IIRC Rogers was following the standard deviations of the normal distribution but wasn't without merit in finding common characteristics within said group. But def incorrect as written in the article.