My Excel (2013) returns exactly what R does. I used both T.INV and T.INV.T2 There is no TINV. Has Excel been updated?
Duncan Murdoch <murdoch.dun...@gmail.com> Sent by: r-help-boun...@r-project.org 09/30/2014 02:36 PM To Andre <geomodel...@gmail.com>, cc r-help@r-project.org Subject Re: [R] Inverse Student t-value On 30/09/2014 2:26 PM, Andre wrote: > Hi Duncan, > > Actually, I am trying trace the formula for the "Critical value of Z" > and manual formula is > =(I7-1)/SQRT(I7)*SQRT((TINV(0.05/I7,I7-2))^2/(I7-2+TINV(0.05/I7,I7-2))) > > So, I got new problem for TINV formula. I just need a manual equation > for TINV. Sorry, can't help. I'm not sure I understand what you want, but if it's a simple formula for quantiles of the t distribution, it doesn't exist. Duncan Murdoch > > Hope solve this problem. > > Cheers! > > > On Wed, Oct 1, 2014 at 1:20 AM, Duncan Murdoch > <murdoch.dun...@gmail.com <mailto:murdoch.dun...@gmail.com>> wrote: > > On 30/09/2014 2:11 PM, Andre wrote: > > Hi Duncan, > > No, that's correct. Actually, I have data set below; > > > Then it seems Excel is worse than I would have expected. I > confirmed R's value in two other pieces of software, > OpenOffice and some software I wrote a long time ago based on an > algorithm published in 1977 in Applied Statistics. (They are > probably all using the same algorithm. I wonder what Excel is doing?) > > N= 1223 > alpha= 0.05 > > Then > probability= 0.05/1223=0.0000408831 > degree of freedom= 1223-2= 1221 > > So, TINV(0.0000408831,1221) returns 4.0891672 > > > Could you show me more detail a manual equation. I really > appreciate it if you may give more detail. > > > I already gave you the expression: abs(qt(0.0000408831/2, > df=1221)). For more detail, I suppose you could look at the help > page for the qt function, using help("qt"). > > Duncan Murdoch > > > Cheers! > > > On Wed, Oct 1, 2014 at 1:01 AM, Duncan Murdoch > <murdoch.dun...@gmail.com <mailto:murdoch.dun...@gmail.com> > <mailto:murdoch.dun...@gmail.com > <mailto:murdoch.dun...@gmail.com>>> wrote: > > On 30/09/2014 1:31 PM, Andre wrote: > > Dear Sir/Madam, > > I am trying to use calculation for two-tailed inverse > of the > student`s > t-distribution function presented by Excel functions like > =TINV(probability, deg_freedom). > > For instance: The Excel function > =TINV(0.0000408831,1221) = returns > 4.0891672. > > Would you like to show me a manual calculation for this? > > Appreciate your helps in advance. > > > That number looks pretty far off the true value. Have you > got a > typo in your example? > > You can compute the answer to your question as > abs(qt(0.0000408831/2, df=1221)), but you'll get 4.117. > > Duncan Murdoch > > > > > ______________________________________________ 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]] ______________________________________________ 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.
