Re: T-Student question

[Asier <haxier at softhome dot net>]

El 29/04/2003, Martin Jansche escribió:

> No.  That gives you the *density* at 2.11.

Oops! Sorry O:)

> You're asking for the inverse CDF, I assume.  Are you sure you need
> it?  In many applications you ultimately want to know whether you can
> reject the null-hypothesis and at what p-value.  If you do your
> calculcations from tables, then critical values of x are useful.  But
> otherwise, what do you need them for?

My mathematical knowledge is near zero compared to yours O:)

I've two vectors of means and variances (from a normal distribution)
calculated from a matrix of data.  (from each column of the matrix I
calculate one mean and one variance) and I must give each one a confidence
interval.

I must know that t_(n-1;\alpha). I usually have seen this data in
tables like this:

"T Student Distribution" 

        P (t <= t_p) = p

Degrees     t_0.995       t_0.99  (...)

   1          63,66         31,82  ...
   2           9,92          6,96  ...
  ...          ...           ...   ...

Like in http://helios.bto.ed.ac.uk/bto/statistics/table1.html

I need to know how to calculate this kind of tables. If I know the degrees of
freedom and the probability, I want to calculate the data in the table.

I think I'll have the same problem with the Pearson's chi-square function
when I'll try to calculate the interval for the variance. I have a similar
table ("pearson chi-square distribution table"), and the same need so if yo
know how... :)))))

Hmmm my english is really poor. I've been writting this for 30 minutes!
(you know spanish??)
--
Asier ·· NO A LA GUERRA, NO EN MI NOMBRE ·· [ Socio Co-Fundador del K.T.P ]