I love mathematics.
I love language.
I love Garrison Keillor's rambling annecdotes of Lake Wobegone.

So what could be better than this from Language Log?

17% in the 95th percentile, eh?

I don't get it.

The 95th percentile of anything is the range into which ninety five percent fit and five percent don't.

The article says that there are 17% of children under 20 who are in that 5%.

And the Lake Wobegone reference is that in his introduction to his stories Keillor always referred to it as a place where "all the children are above average".

Just as mathematically impossible.

I read all the comments and there were a lot of meanderings there. I used to teach nutrition, so I know a little about this. (My dissertation was measuring energy expenditure in critically ill patients on ventilators.) Those saying that the BMI is very unreliable in kids under 20 are accurate.

Being in the 95th percentile means that the 17% are in the top 5th percentile of children of the same age and sex, so that doesn't make sense. The "normal" weight child would be at 50% of his/her age and gender.