On 07-Nov-09 09:02:38, huaru wang wrote: > Hello, every one, > > Using the qt() function in R, I got a different Student t-value > with the Student t table. > e.g. the return value of function qt(0.95,9) is 1.833, while in > table it is 2.262. > > I do not know why the difference exists. I guess it may be a bug > in R. > --
Not at all. The reason is that your table gives the t-value for a two-sided test (with equal tails), i.e. 0.025 in each tail. The function qt() in R returns the t-value for a one-sided test, i.e. 0.05 in the (by default) upper tail. Compare: qt(0.95,9) # [1] 1.833113 qt(0.975,9) # [1] 2.262157 The second value agrees with your table. Many printed tables give the two-sided values, rather than the one-sided. Hoping this helps, Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <ted.hard...@manchester.ac.uk> Fax-to-email: +44 (0)870 094 0861 Date: 07-Nov-09 Time: 09:55:50 ------------------------------ XFMail ------------------------------ ______________________________________________ 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.
