[R] Solving a normal distribution pnorm for q

[Berend Hasselman]

On 12-12-2013, at 14:56, Johannes Radinger <johannesradinger at gmail.com> wrote:

> Hi,
> 
> 
> 
> I found follwowing example of pnorm here:
> 
> http://www.r-tutor.com/elementary-statistics/probability-distributions/normal-distribution
> 
> 
> 
> Problem
> 
> Assume that the test scores of a college entrance exam fits a normal
> distribution. Furthermore, the mean test score is 72, and the standard
> deviation is 15.2. What is the percentage of students scoring 84 or more in
> the exam?
> 
> 
> 
> Solution
> 
>> pnorm(84, mean=72, sd=15.2, lower.tail=FALSE)
> 
> [1] 0.21492
> 
> 
> 
> That is straight forward, however what if I want to know the score the best
> 30% students are reaching at least. So I know the solution of pnorm but
> want to know its q. How can that be achieved in R?
> 
> 
> 
> Any suggestions?


Do

?pnorm

in R. You are directed to a help page where you will also see “qnorm”.
Then try qnorm.

Berend