Thanks for the fast response. Of course I totally overlooked qnorm as I had a more complex task in my head.
I wanted to reverse following equation: r=0.67 q=-150 sd1=100 sd2=1000 X <- pnorm(q=q,sd=sd1)*r+pnorm(q=q,sd=sd2)*(1-r) Maybe its mathematically really easy, but somehow I don't get it how to do reverse and provide X and get q especially with the presence of r respectively as weighting factors for the two distributions. /J On Thu, Dec 12, 2013 at 3:09 PM, Dániel Kehl <ke...@ktk.pte.hu> wrote: > Looks like homework. > > Try ?qnorm > ________________________________________ > Feladó: r-help-boun...@r-project.org [r-help-boun...@r-project.org] ; > meghatalmazó: Johannes Radinger [johannesradin...@gmail.com] > Küldve: 2013. december 12. 14:56 > To: R help > Tárgy: [R] Solving a normal distribution pnorm for q > > 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]] > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > [[alternative HTML version deleted]]
______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
