Congrats on the invite jenniferlc53! With regards to your question, Yale interviews about half of their applicants. Then they admit about half (just over-it was 56% last year) of those who were interviewed. I got this info from Business Week's profile of Yale for 2005. Info is below:
In 2005, the B-school interviewed 51% of its full-time MBA applicants, and 99% of its admitted applicants. 2,033 people applied to the full-time MBA program in 2005. The school accepted 28% (selectivity) of those applicants, and 37% of admitted applicants (yield) enrolled in the program.