Ah, I thought this smelled like homework... Please read the R-help mailing list posting guide (http://www.r-project.org/posting-guide.html), specifically:
"Basic statistics and classroom homework: R-help is not intended for these." On Mon, May 18, 2009 at 10:35 AM, Kon Knafelman <konk2...@hotmail.com> wrote: > Hey, > > when i type in either of those formulas into R, i dont really get the answer > im looking for. For such large samples, isnt the sample variance meant to > approach the actual variance, which is 1 for a standard normal? > > also, when i use sapply, i 1000 results for variance, where i think i just > need one number. > > I've worked on this problem for so long. The initial problem is as follows > > "Use the simulation capacity of R to generate m = 1 000 > samples of size n = 15 from a N(0,1) distribution. Compute the statistic > (n-1)S^2/σ^2 for the normally generated values, labelling as NC14. Produce > probability histogram for NC14 and superimpose the theoretical distribution > for a χ2 (14 degrees of freedom)" > >> g=list() >> for(i in 1:1000){z[[i]]=rnorm(15,0,1)} > >> for (i in 1:1000)vars[[i]] = sum(z[[i]]) > >> vars[[i]] > >> sum(var(z[[i]])) > > [1] 0.9983413 > > Does this make sense? my logic is that i use the loop again to add up all > the individual variances. im not really sure if i did it correctly, but if > someone could make the necessary corrections, i'd be very very greatful. > > Thanks heaps guys for taking the time to look at this > >> Date: Mon, 18 May 2009 15:06:47 +0200 >> From: waclaw.marcin.kusnierc...@idi.ntnu.no >> To: konk2...@hotmail.com >> CC: mike.lawre...@dal.ca; r-help@r-project.org >> Subject: Re: [R] sample variance from simulation >> >> Mike Lawrence wrote: >> > why not simply >> > >> > vars=list() >> > for (i in 1:1000) vars[[i]] = var(z[[i]]) >> > >> > >> >> ... or, much simpler, >> >> vars = sapply(z, var) >> >> vQ > > ________________________________ > Let ninemsn property help Looking to move somewhere new this winter? -- Mike Lawrence Graduate Student Department of Psychology Dalhousie University Looking to arrange a meeting? Check my public calendar: http://tr.im/mikes_public_calendar ~ Certainty is folly... I think. ~ ______________________________________________ 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.