The Isaac Curse is Real...

The Issac Curse is real, kind of.

The "Isaac Curse" is a pattern (identified by a friend named Isaac, or at least that's one of his many names) found in Carolina sporting events when one team is supposed to win 80% of the time (+/- 5%) and the opposite occurs (the underdog wins). These pregame probabilities were either from my Aggregate Model for NCAAF or a combination of the Aggregate and KenPom for NCAAB. For the 2013-14 school year, this seemed to happen every single time:

• ECU (UNC 79.95%, lost) in football 
• Belmont (UNC 81.49%, lost) Louisville (UNC 20.90%, won), UAB (UNC 82.94%, lost), Michigan State (UNC 17.06%, won), Texas (UNC 81.55%, lost) in basketball

Of course, I found this was another case of misremembering when I actually looked at the data. The 80% ± 5% pregame probability also occurred in 2013-14 with Virginia, Miami, Virginia Tech, Georgia Tech, and South Carolina in football, and Virginia, NC State, Maryland, Virginia Tech, and Duke in basketball, and the favorites all won.

So we can adapt the Isaac Curse to simply mean that underdogs win at a rate higher than their 20% chances imply. I looked at all instances over the past 2 years in which I have seen the favorite meet the 80% ± 5% criteria. In NCAAF, the underdog was 2-8: a win percentage of exactly .200. No Isaac Curse there. But for NCAAB, the underdog was 8-9: winning 47.06% of the time. Using the expectation of 20%, the underdog should have won 3.4 of those 17 games, and in fact won over twice that: 8.

Calculating a t-score for this sample resulted in t = 2.71, with an associated p-value = 0.9923. Continuing with the Isaac theme, his favorite number is 8 (which is why every 8 in this post is highlighted), so at α = 0.008, we can conclude that the Isaac Curse exists, at least for NCAAB: underdogs win at a higher rate than their 20% chances imply. Why is this; is it due to limitations in the models? That question I can't answer so simply. 

But it's a good thing the Curse is real: Duke is supposed to win 78% of the time tonight, per KenPom. Come on Isaac Curse!