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The percentiles for each score are routinely outputted using the frequency procedure in SPSS. The percentages of people with scores equal or below each observed score can be obtained by running the below in SPSS.
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In R the percentages of people with scores equal or below each observed score can be obtained by running or the below in R:

How do I find out how many people have a score above a certain value?

Percentiles give the percentage of people who have a score below a threshold score.

Percentile (score) = 100 $$\frac{\mbox{n} \leq \mbox{score}}{\mbox{N}}$$

100 - Percentile (score) = 100 $$\frac{\mbox{n} \gt \mbox{score}}{\mbox{N}}$$

The percentages of people with scores equal or below each observed score can be obtained by running the below in SPSS.

FREQUENCIES VAR=SCORE.
EXE.

or the below in R:

score <- sort(score)
perc <- rep(-99,length(score))
ict <- 1
b <- duplicated(score)
for (ict in 1:length(score) {
for (i in score) {
perc[ict] <- 100*sum(score<=i)/length(score)
ict <- ict+1
}
 }
(percu <- perc[!duplicated(perc)])
(scoreu <- score[!duplicated(score)])
percu
scoreu

None: FAQ/perc (last edited 2013-03-08 10:17:13 by localhost)