BYU has 29 appearances in 81 tournaments = 36% (roughly 1 out of 3)
BYU has 15 wins in 81 tournaments = 19% (just under 1 out of 5)

BYU has 12 tournaments out of 29 where they won at least one game (41%)

BYU has the 24th most appearances in the tournament; they also have the most appearances without making it to the Final Four.

In the last 40 years:

21 appearances, 8 with at least one 1 win (appearance 52% of their seasons and a win every 5 years)

In the last 20 years

12 appearances, 3 with at least 1 win (appearance 60% of their seasons and a win every 6 years)