[R] Solving a normal distribution pnorm for q

Jeff Newmiller jdnewmil at dcn.davis.CA.us
Thu Dec 12 15:20:41 CET 2013


?pnorm ... carefully...
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Sent from my phone. Please excuse my brevity.

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?
>
>
>
>/Johannes
>
>	[[alternative HTML version deleted]]
>
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