Golf entry: mean( replicate( 10000, t.test(rnorm(10, 0.1, 1), alternative='greater', mu=0, conf.level=0.95)$p.value < 0.05))
Or mean( replicate( 10000, t.test(rnorm(10, .1), a='g')$p.value < .05)) or even mean( replicate( 10000, t.test(rnorm(10, .1), a='g')$p. < .05)) -- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare greg.s...@imail.org 801.408.8111 > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r- > project.org] On Behalf Of Joris Meys > Sent: Thursday, May 06, 2010 9:57 AM > To: Dimitri Liakhovitski > Cc: r-help@r-project.org; level > Subject: Re: [R] T-test & for loop > > Hehe, > > those homeworks. If you can explain this code to the professor, you > surely > passed. > > n <-10000 > obs.rej.rate <- sum(sapply(1:n,function(x){t.test(rnorm(10, 0.1, > 1),alternative="greater",mu=0,conf.level=0.95)$p.value <0.05}))/n > obs.rej.rate > > This could actually be another round of R-golf. Anybody up to it? > > > > On Thu, May 6, 2010 at 3:03 AM, Dimitri Liakhovitski > <ld7...@gmail.com>wrote: > > > Sounds like homework (you are not supposed to post homework-related > > questions here - read the guidelines). But anyway: > > > > nr.of.rejections=0 > > for(i in 1:10000){ > > x=rnorm(10, 0.1, 1) > > result<- > t.test(x,alternative="greater",mu=0,conf.level=0.95)$p.value > > if(result<0.05) nr.of.rejections = nr.of.rejections+1 > > } > > print(paste("Observed number of rejections of Ho:", nr.of.rejections, > sep=" > > ")) > > observed.rejection.rate = nr.of.rejections/10000 > > print(paste("Actual rejection rate of Ho:", observed.rejection.rate, > sep=" > > ")) > > > > However, it's not Type 1 error rate. It's the observed rejection > rate. Type > > 1 error is probability of rejecting Ho when it is actually TRUE. And > in > > your > > case (x = rnorm(10,0.1,1) your null hypothesis (that mean = 0) is NOT > true > > because,as you know, in the population the mean is 0.1. > > > > Dimitri > > > > > > On Wed, May 5, 2010 at 2:31 PM, level <lev_lamb...@hotmail.co.uk> > wrote: > > > > > > > > I have been set a question which i understand statistically but my > > > inability > > > with R is preventing me from finishing it.. > > > > > > My question is that we to calculate the frequency of Type 1 errors > > > > > > starting with x = rnorm(10, 0.1, 1) > > > > > > then doing a t-test seeing whether you reject the null hypothesis > (Ho > > mu > > > = > > > 0) alternative is mu > 0 > > > > > > Then i am supposed to use a for loop to do this procedure 10 000 > times > > > keeping track whether the null has been rejected or not. If anyone > can > > > help > > > with me it would be great help > > > > > > cheers > > > > > > -- > > > View this message in context: > > > http://r.789695.n4.nabble.com/T-test-for-loop- > tp2131458p2131458.html > > > Sent from the R help mailing list archive at Nabble.com. > > > > > > ______________________________________________ > > > 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. > > > > > > > > > > > -- > > Dimitri Liakhovitski > > Ninah.com > > dimitri.liakhovit...@ninah.com > > > > [[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. > > > > > > -- > Joris Meys > Statistical Consultant > > Ghent University > Faculty of Bioscience Engineering > Department of Applied mathematics, biometrics and process control > > Coupure Links 653 > B-9000 Gent > > tel : +32 9 264 59 87 > joris.m...@ugent.be > ------------------------------- > Disclaimer : http://helpdesk.ugent.be/e-maildisclaimer.php > > [[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. ______________________________________________ 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.