Is there a quick way to convert z-scores into percentile scores?

Question

Does anyone know of a function or R package that can help me turn z scores into percentile scores? The final goal is to classify or rank a group of respondents into four categories based on the heights of their z scores (20% lowest scores, 30%, 30%, 20% highest scores).

Any ideas? Many thanks in advance!

With what assumptions on the original scores? How are the values scaled - are the z-scores computed from sample mean and sample std deviation or from some known/assumed values? — Glen_b, Apr 14 '13 at 10:13
The original scores are raw test scores before i normalized them by using scale(x) — rdatasculptor, Apr 14 '13 at 10:17
chl, thanks! I initially missed that ont, but it turned out to be very helpful. — rdatasculptor, Apr 22 '13 at 18:21

score 16 · Accepted Answer · answered Mar 30 '14 at 18:36

16

pnorm(z) will do it.

> pnorm(1.96)
[1] 0.9750021
> pnorm(0)
[1] 0.5
> pnorm(-1)
[1] 0.1586553

Or if you insist on a percentile, boom. Then try

round(pnorm(1.96)*100,0)

answered Mar 30 '14 at 18:36

Farrel

740

1

The usual 95% confidence interval is given by pnorm(1.96) - pnorm(-1.96) with result 0.9500042 – PatrickT Nov 14 '17 at 14:50

Is there a quick way to convert z-scores into percentile scores?

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