On 19-Oct-04 pcscan wrote: > We are currently using the t-test in Package stats, > [...] > but have some troubles : > 1. why does the t-test take so a long time to perform a single test > on a row of a data.frame ? Is there any alternative function to > perform t-test on all the rows of a data.frame ?
Not sure what your problem is here. 't.test' is almost instantaneous on my somewhat slow machine here. > 2. We got different results on the following data with the argument > var.equal setting as TRUE and FALSE respectively. > We are curious why the "Welch Two Sample t-test" couldn't > distinguish these two vectors well. The two samples have very different standard deviations, the SD of y being about 18 times that of x. You would expect the Welch test to give quite different results from the "var.equal=TRUE" case. In these circumstances I would trust the Welch test rather than the other. Best wishes, Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <[EMAIL PROTECTED]> Fax-to-email: +44 (0)870 094 0861 [NB: New number!] Date: 19-Oct-04 Time: 08:27:01 ------------------------------ XFMail ------------------------------ ______________________________________________ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
