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Mistakes When Averaging

When people try to predict football games they often fall
into a trap of their own making. That trap is called averaging. When two
numbers are averaged together, they sometimes cause false results. When two
teams are playing, many handicappers try to predict the final score so they can
make an informed decision on which team to bet on. To arrive at a score they
average the two teams together, comparing offense to the defense.

Averaging two numbers when the numbers are on different
sides of average works ok. The trouble happens when both numbers are on the
same side of average. That may be a hard concept to visualize, but after a
couple examples it should become clear.

The average number of points scored by a team in the NFL
during the 2014 NFL season was 22.7 which can be rounded up to 23. If team A comes
into the game scoring on average 34 points a game and team B comes in allowing
10 points a game, averaging the totals together gives a result of 22 points scored
for team A. (34+10=44. Divided by 2 equals 22.) One team scores above the
league average of 23 and the other team allows below the league average of 23,
so that works well and gives a good result.

If team C comes in scoring 34 points a game and team D comes
in allowing 28 points a game, averaging the totals together would give a result
of team C scoring 31 points, which is less than what they normally score. That just
doesn’t make sense. Team C comes into the game with a really good offense that
scores well above average, and when faced with a poor defense that allows more
than average, why would they be predicted to score less than they normally do?

The problem is both teams are on the same side of the league
average, which gives false results. It makes good teams seem worse and bad
teams seem better. The fix is simple enough. Add the two scores together and
subtract the NFL average to get a good prediction.

Using teams C and D, the better number is calculated like
this:

34+28=62.

62-23(The league
average.)=39.

Where averaging gave
a score of 31 for team C, subtracting the league average gives a score of 39, a
huge difference of 8 points. To get consistently better results, don’t average
numbers together to make predictions in the NFL.

Here’s a full game mock up to illustrate the difference. These
numbers are just an example and we’ll use the Seahawks and Lions for the teams.

The Seahawks come in with a season average game score of 31-24,
the Lions come in with a season average of 20-27. When using averaging, the
result is a predicted score of the Seahawks winning 29-22. (31+27=58/2=29 for
the Seahawks and 20+24=44/2=22 for the Lions.) When using the recommended
method, the predicted score becomes Seahawks winning by 35-21. (31+27-23=35 for
the Seahawks and 24+20-23=21 for the Lions.) Using the average, the Seahawks
are predicted to win the game by 7 points. Using the correct method I’ve laid
out, the Seahawks are predicated to win by 14 points. If the Seahawks were a 10 point favorite, a
handicapper could be fooled into thinking the Lions were a good bet if he
averaged the numbers. Using the correct method, the Seahawks are the clear
choice.

Averaging when comparing teams is a very common mistake and
also one of the costliest. Be aware and beware.