Lester,
I should give a fuller answer as this comes up from time to time on the forum. Basically, is there a good reason for the stat they are giving? If there is a good theory behind it, it might be worth something. Otherwise, it's just statistical noise-data mining. Given enough numbers on anything, you'll find a few weird subsets that work for no apparent reason.
Here's an example of theory...IIRC, in NCAAF bowl games, teams favored by over 7.5 points are only 38% ATS since 1980. The idea is that these teams are usually in bowl games that they are less motivated to play. The other team better prepares and is more dedicated to the game over the 3 week pre-bowl practice span. The favorite is usually quite happy with their season and has nothing left 'to prove.' The underdog is still fighting for respect.
Now, obviously, the theory is just general as not everygame will fit that case (for instance, a big favorite for a national title game should be pretty focused). However, it does make some intuitive sense and is a theory that one could have
before looking at the data to confirm it.
I guess that is the test in my eyes. Is this a relation that one could theoretically expect
before looking at the data? If so, it might have some merit. If not, it's probably just a result of data mining and searching for patterns---such as Sklansky's book talking about Super Bowl Champs poor ATS record in week 2 the following season.
Load up those bets against the Colts