Re: [R] Permutation or Bootstrap to obtain p-value for one sample

2011-10-09 Thread peter dalgaard
On Oct 8, 2011, at 16:04 , francy wrote: Hi, I am having trouble understanding how to approach a simulation: I have a sample of n=250 from a population of N=2,000 individuals, and I would like to use either permutation test or bootstrap to test whether this particular sample is

Re: [R] Permutation or Bootstrap to obtain p-value for one sample

2011-10-09 Thread peter dalgaard
On Oct 9, 2011, at 12:00 , francesca casalino wrote: Thank you very much to both Ken and Peter for the very helpful explanations. Just to understand this better (sorry for repeating but I am also new in statistics…so please correct me where I am wrong): Ken' method: Random sampling of

Re: [R] Permutation or Bootstrap to obtain p-value for one sample

2011-10-09 Thread francesca casalino
Thank you very much to both Ken and Peter for the very helpful explanations. Just to understand this better (sorry for repeating but I am also new in statisticsÂ…so please correct me where I am wrong): Ken' method: Random sampling of the mean, and then using these means to construct a

Re: [R] Permutation or Bootstrap to obtain p-value for one sample

2011-10-09 Thread Bert Gunter
I may be speaking out of turn here, but I would prefer not to see R-help turn into a tutorial site for basic statistics.Such sites already exist (e.g. http://stats.stackexchange.com/). I realize that there is occasionally reason to venture down this path a way within legitimate R contexts, but

Re: [R] Permutation or Bootstrap to obtain p-value for one sample

2011-10-09 Thread Tim Hesterberg
I'll concur with Peter Dalgaard that * a permutation test is the right thing to do - your problem is equivalent to a two-sample test, * don't bootstrap, and * don't bother with t-statistics but I'll elaborate a bit on on why, including * two approaches to the whole problem - and how your

Re: [R] Permutation or Bootstrap to obtain p-value for one sample

2011-10-09 Thread francesca casalino
Dear Peter and Tim, Thank you very much for taking the time to explain this to me! It is much more clear now. And sorry for using the space here maybe inappropriately, I really hope this is OK and gets posted, I think it is really important that non-statisticians like myself get a good idea of

[R] Permutation or Bootstrap to obtain p-value for one sample

2011-10-08 Thread francy
Hi, I am having trouble understanding how to approach a simulation: I have a sample of n=250 from a population of N=2,000 individuals, and I would like to use either permutation test or bootstrap to test whether this particular sample is significantly different from the values of any other

Re: [R] Permutation or Bootstrap to obtain p-value for one sample

2011-10-08 Thread Ken Hutchison
Hi Francy, A bootstrap test would likely be sufficient for this problem, but a one-sample t-test isn't advisable or necessary in my opinion. If you use a t-test multiple times you are making assumptions about the distribution of your data; more importantly, your probability of Type 1 error will