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I have a feeling there's only one way to say this: you can be in the “95th percentile”. A colleague of mine says it's OK to say “the 95% percentile”, which doesn't seem to make mathematical sense to me.

What's correct?

Jean-Philippe Pellet
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    Stick to your intuition: you're correct and your colleague is wrong. Their version is not only tautological, it sounds ridiculous when spoken: the ninety-five per cent percentile. – Chappo Hasn't Forgotten Nov 20 '18 at 21:31

1 Answers1

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Percentiles, whether we mean rank or range, are discussed using ordinal numbers: first, 50th, 95th, etc. To say "ninety-five percent percentile" would be considered an error in any kind of formal or academic setting, as well as being redundant.

Percentile ranks are reported on an ordinal scale.

Applied Statistics in Education and Psychology I

Michael Harvey
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    Not to mention that percent literally means "out of a hundred," so 95 out of 100 out of a further hundred is a statement best left to actuaries. – IchabodE Nov 20 '18 at 21:30
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    I think even an actuary would struggle. They could deal with the 95 out of a hundred out of a hundred. But this is not just 95 out of a hundred but the ordinal of 95 out of a hundred, so it means the 0.95th percentile. Only a philosopher of mathematics would think about that and then only if they were having trouble sleeping. – David Robinson Nov 20 '18 at 22:36