[R] Normal distribution with R

Eik Vettorazzi E.Vettorazzi at uke.uni-hamburg.de
Wed Apr 29 21:06:40 CEST 2009


Hi James
its just simple calculus, since with
q90<-qnorm(.9,me,sd)
q10<-qnorm(.1,me,sd)

mean<-(q90+q10)/2    # the normal distribution is symmetric around the mean
sd<-(q90-q10)/ (qnorm(.9)-qnorm(.1)) #  between 10th and 90th are 
qnorm(.9)-qnorm(.1)=2.563103sds

hth.

guox at ucalgary.ca schrieb:
> If we knew two pth quantiles for a normal distribution,
> is it possible that we can find mean and sigma for the normal distribution
> using R?
>
> Let x ~ norm(mean, sigma).
> Suppose that qnorm(0.9,mean,sigma) and qnorm(0.1,mean,sigma) are known.
> Can we find mean and sigma using R?
>
> Thanks,
>
> -james
>
> ______________________________________________
> R-help at 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.
>   

-- 
Eik Vettorazzi
Institut für Medizinische Biometrie und Epidemiologie
Universitätsklinikum Hamburg-Eppendorf

Martinistr. 52
20246 Hamburg

T ++49/40/42803-8243
F ++49/40/42803-7790




More information about the R-help mailing list