Function of qnorm() in R

Question

I have read the documentation on qnorm() but could not really understand what it does. Can you please answer in detail what qnorm() does?

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Answer 1

"The idea behind qnorm is that you give it a probability, and it returns the number whose cumulative distribution matches the probability. For example, if you have a normally distributed random variable with mean zero and standard deviation one, then if you give the function a probability it returns the associated Z-score"

from http://www.cyclismo.org/tutorial/R/probability.html

You can further refer to the above link to read up more on the same.

Answer 2

The function qnorm() aims to find the boundary value, A in P(X < A), given the probability P.

For example, suppose you want to find the 85th percentile of a normal distribution whose mean is 70 and whose standard deviation is 3. Then you ask for:

qnorm(0.85,mean=70,sd=3)
[1] 73.1093

From https://cran.r-project.org/web/packages/tigerstats/vignettes/qnorm.html