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. -- Íõ»¯Èå ²©Ê¿Ñо¿Éú ±±¾©Ê¦·¶´óѧ¾°¹ÛÉú̬Óë¿É³ÖÐøÐÔ¿ÆѧÑо¿ÖÐÐÄ ±±¾©Êк£µíÇøнֿÚÍâ´ó½Ö19ºÅ±±¾©Ê¦·¶´óѧÉúÃü¿ÆѧѧԺ 100875 Huaru Wang PhD Candidate, CLESS, College of Life Science, Beijing Normal University Tel: 010 - 5880 5812 Cell phone:189 0137 6067 No.19 Xinjiekouwai Street, Beijing 1000875 [[alternative HTML version deleted]]
Hi Huaru, Are you sure you are looking at 0.95 and NOT 0.975? as qt(0.975,9) = 2.262 generally tables are given for alpha/2 (alpha=0.05 in your case) significance. Please check carefully. Thx, S. On Sat, Nov 7, 2009 at 4:02 AM, huaru wang <huaru.wang@gmail.com> 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. > -- > Íõ»¯Èå ²©Ê¿Ñо¿Éú > ±±¾©Ê¦·¶´óѧ¾°¹ÛÉú̬Óë¿É³ÖÐøÐÔ¿ÆѧÑо¿ÖÐÐÄ > ±±¾©Êк£µíÇøнֿÚÍâ´ó½Ö19ºÅ±±¾©Ê¦·¶´óѧÉúÃü¿ÆѧѧԺ 100875 > Huaru Wang > PhD Candidate, CLESS, College of Life Science, Beijing Normal University > Tel: 010 - 5880 5812 > Cell phone:189 0137 6067 > No.19 Xinjiekouwai Street, Beijing 1000875 > > [[alternative HTML version deleted]] > > > ______________________________________________ > 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. > >[[alternative HTML version deleted]]
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.Harding at manchester.ac.uk> Fax-to-email: +44 (0)870 094 0861 Date: 07-Nov-09 Time: 09:55:50 ------------------------------ XFMail ------------------------------