[R] Simulate values

Greg Snow 538280 at gmail.com
Tue Apr 7 17:57:59 CEST 2015

Thanks for your final paragraph, we sometimes see people who want us
to do their homework for them and that does not go over well, but I
think you situation is one where many would be happy to help.  So here
are some hints to help:

The rnorm command expects the standard deviation, not the variance, so
to generate normals with variance equal to 25 you need to specify the
square root (5) as the 3rd argument.

The rep command will just repeat the 40 random number 500 times, not
generate new ones, so you will have the exact same sample (and all in
one long vector).  There are a few different ways to do this, but for
easiest understanding I would suggest using the replicate function,
this function will run a set of code the requested number of times, so
think about how you would generate your data and compute the test
statistic from the generated data, then pass that code to the
replicate function (if it is more than 1 line then use curly brackets
({}) to group the lines of code) to generate your 500 test statistics.

On Mon, Apr 6, 2015 at 4:52 PM, Osiris10101 <osiris94 at gmx.ch> wrote:
> Hello,
> I'm facing the following task:
> Simulate 500 values of the statistic (n-1)s^2/sigma^2 based on taking 500
> samples of size n=40
> from the N(mu=10; sigma^2 = 25) distribution.
> I think with the following command:
> rep(rnorm(40,10,25),times=500)
> I was able to simulate the samples but how I now can simulate the values of
> the chi-square-distribution is a mystery to me...
> I hope anyone can help me, shouldn't be a big problem...
> Thanks in advance!
> Reason for posting:
> I started a course at the University of Manchester and had to catch up with
> R, which I never used back in Switzerland. Now I'm solving some exercises to
> get more practice and this is one of them.
> --
> View this message in context: http://r.789695.n4.nabble.com/Simulate-values-tp4705574.html
> Sent from the R help mailing list archive at Nabble.com.
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Gregory (Greg) L. Snow Ph.D.
538280 at gmail.com

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