During today’s Aston Villa-Manchester United match, Iain Dowie (the color commentator) mentioned that United’s form is improving and that they are historically a stronger team in the second half of the season, meaning that they may be able to put this season’s troubles behind them and make a run either the title or a Champions League spot. I didn’t get a chance to record the exact statement, but I decided to check up on it regardless.
I pulled data from the last ten completed Premier League seasons (via statto.com) to evaluate whether there’s any evidence that this is the case. What I chose to focus on was simply the number of first half and second half points for United, with first half and second half defined by number of games played (first 19 vs. last 19). One obvious problem with looking at this so simply is strength of schedule considerations. However, the Premier League, by virtue of playing a double round robin, is pretty close to having a balanced schedule—there is a small amount of difference in the teams one might play, and there are issues involving home and away, rest, and matches in other competitions, but I expect that’s random from year to year.
So, going ahead with this, has Man U actually produced better results in the second half of the season? Well, in the last 10 seasons (2003-04 – 2012-13), they had more points in the second half 4 times, and they did worse in the second half the other 6. (Full results are in the table at the bottom of the post.) The differences here aren’t huge—only a couple of points—but not only is there no statistically significant effect, there isn’t even a hint of an effect. Iain Dowie thus appears to be blowing smoke and gets to be the most recent commentator to aggravate me by spouting facts without support. (The aggravation in this case is compounded by the fact that this “fact” was wrong.)
I’ll close with two oddities in the data. The first is that, there are 20 teams that have been in the Premiership for at least 5 of the last 10 years, and exactly one has a significant result at the 5% level for the difference between first half and second half. (Award yourself a cookie if you guessed Birmingham City.) This seems like a textbook example of multiplicity to me.
The second, for the next time you want to throw a real stumper at someone, is that there is one team in the last 16 years (all I could easily pull data for) that had the same goal difference and number of points in the two halves of the season. That team is 2002-03 Birmingham City; I have to imagine that finishing 13th with 48 points and a -8 goal difference is about as dull as a season can get, though they did win both their Derby matches (good for them, no good for this Villa supporter).
|Year||First Half Points||Second Half Points||Total Points||First Half Goal Difference||Second Half Goal Difference||Total Goal Difference|