0

I apologize if this question is exceedingly simple, but I did not find the answer here on Cross Validated or on https://en.wikipedia.org/wiki/Percentile or on https://en.wikipedia.org/wiki/68%E2%80%9395%E2%80%9399.7_rule.

For example, imagine I have a normal distribution and I know that its mean is 200 and its standard deviation is 10. No problem for its median and its 1-2-3 standard deviations. How can I calculate the value which corresponds to the 75 percentile? How can I calculate the percentile which corresponds to the value of 75?

Numbers are provided as an example only.

(I use R)

statisticianwannabe
  • 475
  • 1
  • 6
  • 14
  • 3
    To get the 75% quantile, use qnorm(0.75,200,10). To get the percentile for the value of 75, use pnorm(75,200,10). Look at ?qnorm. – Stephan Kolassa Mar 16 '18 at 11:31
  • Thank you for your answer. Can you tell me how can I calculate them manually? – statisticianwannabe Mar 16 '18 at 11:43
  • 3
    There are no closed form solutions for general quantiles or percentiles of the normal distribution. You can look at tables after transforming your setting to a standard normal distribution with mean 0 and SD 1. Or you can integrate numerically. – Stephan Kolassa Mar 16 '18 at 11:45
  • 1
    You can find many answers to this question with this search: https://stats.stackexchange.com/search?q=calculate+normal+quantile – whuber Mar 16 '18 at 14:18

0 Answers0