"percentile" or "centile"? [closed]

I know that both terms exist but I wonder which one would/should be considered (more) correct? Percentile seems an oddball as we also use quantile, decile, quartile, but never perdecile etc.

Solution 1:

Both of them are correct and have the same meaning.

Dictionary.com defines centile as:

noun
(not in technical use) a percentile.

According to Google Ngram Viewer, percentile is much more prevalent.

Solution 2:

According to Stuart and Ord (Kendall's Advanced Theory of Statistics, Fifth Edition, Vol 1, 1987), percentile (and quartile) were terms coined by the creative, innovative and authoritative statistician (amongst many other things) Sir Francis Galton.

Coming from a creative and formative intellect, his term endured in the face of the more consistent term centile, which as you say, parallels quartile, decile and others. Both are correct and both seem widely understood in the statistical literature.

Solution 3:

Which is more correct would depend on style more than anything else.

In theory, you could make a case that cent has more senses than percent, and, therefore, despite centile simply being listed as meaning percentile by some dictionaries, argue for centile actually meaning something different than percentile in the right situation.

But I think that would be a highly uncommon situation, and perhaps even one that was contrived just to make a point. Practically speaking, they mean the same thing.

The choice of which to use is subjective.

As for the mention of perdecile, every word that's been mentioned in the question except for that one comes from an existing base word to which the suffix -ile has been added:

[Merriam-Webster]
adjective suffix
: tending to or capable of
// contractile
noun suffix : segment of a (specified) size in a frequency distribution
// decile

There is no perdecile, because there is no such word as perdec.

Although we have percent, which came from per cent, and the Latin per centum, I'm not aware of any common use of per dec from which perdec would originate and to which -ile would be added.

So using the lack of perdecile as the basis for deciding between percentile and centile is not the right analogy.