Re: [R] Code Verification

2005-07-20 Thread Christoph Buser
Hi t.test assumes that your data within each group has a normal distribution. This is not the case in your example. I would recommend you a non parametric test like wilcox.test if you want to compare the mean of two samples that are not normal distributed. see ?wilcox.test Be careful. Your

Re: [R] Code Verification

2005-07-20 Thread Liaw, Andy
From: Christoph Buser Hi t.test assumes that your data within each group has a normal distribution. This is not the case in your example. Eh? What happen to the CLT? Andy I would recommend you a non parametric test like wilcox.test if you want to compare the mean of two samples that

Re: [R] Code Verification

2005-07-20 Thread Christoph Buser
Dear Andy Since the power of the t-test decreases when there are discrepancies in the data to the normal distribution and there is only a small loss of power if the data is normal distributed, the only reason to use the t.test is his simplicity and the easier interpretation. Generally I'd prefer

[R] Code Verification

2005-07-19 Thread pantd
Hi R Users I have a code which I am running for my thesis work. Just want to make sure that its ok. Its a t test I am conducting between two gamma distributions with different shape parameters. the code looks like: sink(a1.txt); for (i in 1:1000) { x-rgamma(40, 2.5, 10) # n = 40, shape = 2.5,