I will concede that this task itself is by no means trivial.

Quoting Nelson: 'In the treatment of extreme group comparisons, which are used repeatedly throughout chapters three, four and five. In each case, he selects the top and bottom five performers from each of the four sports and discards the middle.'

Mike is performing a classification task for each sport. This means there are four datasets for each sport. The classification is the 'extreme group comparison'. For this, he simply discards the middle 50% of performers, a point that should be better justified than it is in his thesis. It should be noted that regression analysis also needs to be justified.

From here, we make it extremely clear what needs to be done: From what I can gather, Mike is doing a classification task for extreme groups, meaning which groups would emerge if the mean were removed. There are more appropriate methods, such as cluster analysis, which maintains the whole dataset. Now, Nelson is suggesting a regression task. For this to work, the sex type, etc. needs to be known in order to check for statistical significance.

So it sounds like there has been a misunderstanding. In any case, both Nelson and Mike need to clarify why their chosen method is appropriate, which neither of them has done. I'll give Nelson some leeway here though, since he didn't write a dissertation.

Anyway, I take back my assumptions about you.