This post is going to be short and sweet. The takeaway: Andy Reid’s teams do not always improve as the season goes on.

Fans and commentators often repeat the same conventional wisdom that Reid has the Eagles running at peak performance coming down the stretch. Right now, some people are using it to ward away bad feelings about the Eagles’ disappointing first three games. Unfortunately it’s a myth propagated by poor use of statistics.

You might have seen the statistic that Reid is 35-14 in December. But it’s a rather crazy idea to suggest that the month of December somehow brings out the best in the Eagles. What’s so special about that month over others? Let’s look at Reid’s win percentage over the last 12 years by game:

I’ve included the trendline, which makes it look like there’s improvement. But check out the r-squared value. The “improvement” isn’t significant. If there’s any correlation at all, it’s dwarfed by other factors.

You can cherry-pick games 12, 13, and 14 where his win percentage is 75 percent. But (a) over 12 years that result is less than 1 win better than average, and (b) in the bookend games 11 and 15 the team is actually below average. Making any argument based just on those three games is a multiple endpoints problem.

I wouldn’t try to blame Sunday’s game on a typically slow start either. It’s true that week two is the only week where the Eagles have more losses than wins, but until the Giants loss, Reid had won the last 10 week three games.

Above I’ve averaged Reid’s career by point differential, rather than win percentage. This gives more credit to big wins, less credit to close losses, etc. And again, no significant correlation. The wins and losses might as well be distributed at random across all weeks.

Reid is a good coach whose teams have consistently won most of their games. And the team might yet turn things around in 2011. But Reid is no more likely to do better late in the season than he’s doing right now.

Photo from Getty.