= 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 percentiles for each score are routinely outputted using the frequency procedure in SPSS.

{{{
FREQUENCIES VAR=SCORE.
EXE.
}}}

In R the percentages of people with scores equal or below each observed score can be obtained by running

{{{
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
}
 }
perc
score
}}}