[R] problem about finding power in test about variances

Uwe Ligges ligges at statistik.tu-dortmund.de
Thu Apr 30 13:07:29 CEST 2009



ati sundar wrote:
> Hello All
> 
> I am new to this list. I have a problem where for a single sample drawn from normal population, null hypothesis is that variance = k (say).

Perhaps you want to tell us more precisely what you are going to do 
rather than asking the same inprecise question again and again 
(including messages to single persons on the list).
Is k fixed or the variance? What are your data?  Specify a valid Null / 
Alternative combination. If you Null is variance = k (say) then you 
alternative is variance != k or if the alternative is variance > k, then 
your null is probably variance <= k

Uwe Ligges



  Alternative hypothesis is variance > k. Now if we know the true 
variance, then I would like to calculate the sample size required to 
produce certain power (for some
> significance). How do I do this ? I thought of using pwr.chisq.test, and I contacted the author stephane champely, but he said his package can't do this. Does anybody have an idea ?
> 
> Thanks
> Ati
> 
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