ellipse

Dear all,
I'm using the ellipse package and I would like to verify if the
confidence region that I build with this package can be equivalent to  
an Union Intersection Test. I used different value for the t-statistic  
but I can not find the right equivalence.
Does someone know how to choose the right value?

Thanks a lot.
Antonio

Antonio Lucadamo,
Dipartimento di Scienze Economiche e Metodi Quantitativi
Universit? del Piemonte Orientale "A. Avogadro"
via Perrone, 18 - 28100 Novara
fax:          +39 0321 375305
phone:        +39 0321 375338
mobile phone: +39 3385973881
skype contact: antonio.lucadamo