Back in '93, I analyzed a long list of games to determine the probability 
of hitting on a plus 6 bet, assuming the odds of picking a game correctly 
using the spread is 50%.

The analysis is as follows:

Out of 468 possibilities (234 games) there were:

145 plus 6 occurrences

This gives a plus 6 occurrence rate of 31%.

Not bad, you say.  But the important thing is what success rate is needed 
to come out ahead!

Using a binomial probability calculator, in order to come out ahead on a 
plus 6 bet, a success rate of 35% is required!  (fail % = 27% (0 out of 3),
win % = 28% (2 or 3 out of 3)).

Conclusion:  Your odds are better at Black Jack or Craps in Vegas!