# 1st percentile, 2nd percentile… But how to say “2.5th” percentile?

It is necessary for me to write about the 2.5th and 97.5th percentiles of a data set. What is the correct way of writing this?

This post talks about "zeroth", "n-th" and even "epsilonth" as generalisations of the -th suffix, but I haven't found any guidelines for non-integers.

I feel that 2.5th percentile sounds better than 2.5-percentile. Do you agree?

## 2 Answers

There are only one hundred percentiles. You can not be in the 2.5th percentile.

• 25th and 975th permillile? I can only find one English usage of permillile (but several in Latin!) There are quartiles and quintiles and deciles, but I can't find any general term for a k-ile. – Mike Harris Jun 6 '16 at 19:33

I feel that 2.5th percentile sounds better than 2.5-percentile. Do you agree?

Yes I do agree. I would pronounce them 'two point fifth percentile'.

I see that Hot Licks said the same while I was typing.

I'm not sure what I would say with, e.g. 2.25 th.