When ranking CFB secondaries, it's important to diversify the metrics you look at.

Example: The NCAA average of interceptions per passes defended is 19%. If you "defend" a pass, you intercept said pass about 1/5 times.

You can exceed that but variance needs to be warrented.

Here are the top 10 teams that out-performed the NCAA average in interceptions per passes defended:

From those 10 teams, only Florida ranked in the Top 60 of passes defended per game.

These we're considered the "luckiest" intercepting teams in the country (besides maybe UF)

And here are the bottom 10 teams:

If you look just at interceptions as a raw number to come up with a value for a secondary, you'd be discounting quite a few of these teams that should have been much "luckier" than they were.

Pitt ranks 3rd in passes defended per game!

What to take away? If you rank high in PD, high in interceptions and low in Yards/Pass and other metrics - you we're probably a really good secondary.

If there's large variance in there, the data has noise that I don't think is representative of a secondary's actual value.