PS : level, you might want to consider stopping to spam the help-list.
You're not making yourself popular by asking -in one day- 3 questions that
can be solved by using Google and reading the introductions given on the R
homepage.
On Thu, May 6, 2010 at 5:57 PM, Joris Meys <jorism...@gmail.com> wrote:
> 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
>
--
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
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