Pappus' plane - cricket stats

It's useful to check the common wisdom, or things that seem obvious. Often they're true, but sometimes they're not, and even if true, sometimes an analysis reveals surprising related results. This post falls into the latter category.

If a team has good spinners, then their batsmen should do better when playing against spinners. This might be because the country generally produces lots of spinners and so batsmen grow up playing lots of them, or because the batsmen get to practice in the nets against good spinners, or some combination of the two. The same principle should apply to pace bowling.

So let's check. I went to Statsguru and got each of the top eight teams's averages against pacemen, and each team's overall pacemen's average. To start, I considered only the 2000's. The results are plotted below:



That's quite a strong trend, but the direction agrees with the common sense — teams whose pace bowlers have high averages don't score as many runs against pace bowlers, and vice versa. As I said, the trend is very strong, and much of this is due to the luck of world cricket over the past decade. Australia has had excellent batsmen and excellent pacemen, the West Indies the opposite. I repeated the exercise for earlier decades (90's, 80's, and 70's; the results for the 1960's go a bit haywire because three out of the seven teams were weak), and the direction of the trend is the same, but the magnitude varied from a slope of -0.17 to -0.8.

Still, a verification of what we thought we knew, and some ideas of how strong the effect is. Now let's do the same for spinners.



The same basic trend, though with a gentler slope. The results for the earlier decades are similar, with the slopes ranging from -0.3 (the one shown above) to -0.75.

Now let's see if we can get null results. If a team has good pacemen, that should tell us nothing about how well they play spin, right?



Right. No trend at all.

Similarly, if a team has good spinners, that should tell us nothing about how they play pace.



Erm, wrong. Teams with good spinners tend to play pace well. The same trend exists for the earlier decades, with slopes ranging from -0.18 to -0.33 (above). I don't know what the p-value is, but it looks like it's not just luck.

I don't know how to explain this. I have two ideas:
1) learning how to play high-quality spin makes you a better batsman in general;
2) spinners with good pacemen in the team do better than those without, and so the trend is really just "average against pace" v "pace average" in disguise.

I'm inclined to think that the second of these two ideas is a strong factor, but there's no correlation between spin average and pace average in either of the last two decades. For the 2000's:



For the 1980's and 1970's, there is a positive correlation between the two.

From my post on bowler support, a useful rule of thumb in dealing with aggregated data like this is that for every run lower a bowler's teammates' bowling averages are, the bowler's average should go down by a quarter of a run. This works pretty well for the 1980's and 1970's graphs, but doesn't help explain what's going on in the last two decades.

It's a bit of a puzzle, and I don't know what the answer is. Teams that have good spinners tend to play pace well.

(A post-script: I was going to do another post on captaincy today, based on some suggestions from The Atheist, but my regression failed rather miserably. I'll have another try later.)