On May 6, 2010, at 3:51 PM, Greg Snow wrote:
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')$p. < .05))
Having failed with my efforts with:
summary(lm(rnorm(10,.1)~1))[[4]][4] < .05 ....
I'm going to cheat:
mean( replicate( 10^3, t.test(rnorm(10, .1), a='g')$p. < .05))
--
David
--
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
--
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______________________________________________
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--
Dimitri Liakhovitski
Ninah.com
dimitri.liakhovit...@ninah.com
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PLEASE do read the posting guide
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--
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
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______________________________________________
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.
David Winsemius, MD
West Hartford, CT
______________________________________________
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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