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← Revision 21 as of 2013-03-08 10:17:13 ⇥
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| The percentiles for each score are routinely outputted using the frequency procedure in SPSS. | The score percentiles 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: |
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| score <- sort(score) | |
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| a <- rep(-99,length(score)) cc <- rep(-99,length(score)) ict <- 0 kct <- 0 |
ict <- 1 |
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| for (ict in 1:length(score) { for (i in score) { perc[ict] <- 100*sum(score<=i)/length(score) |
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| for (i in score) { perc[i] <- 100*sum(score<=i)/length(score) a[i] <- score[i] kct <- kct+1 if (b[i] == TRUE) { ict <- ict+1 a[ict] <- score[kct] |
} |
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| } perc a cc |
(percu <- perc[!duplicated(perc)]) (scoreu <- score[!duplicated(score)]) percu scoreu |
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 score percentiles 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