Like most sports fans my weekends can include shouting at the radio. Unlike most sports fans I’m usually het up about statistics, not necessarily the performances on the field.
Last weekend it was claimed that the Indian middle order has a weakness against left arm pace in ODIs. I won’t name the individual that said it, because they are an excellent commentator and this isn’t intended to be a criticism of them.
What’s wrong with that claim? Left arm pace bowlers are normally front line bowlers, so are better than the average bowler. That means that when it is said that “X does badly against left arm quicks” we really mean “X is less good against the better bowlers”. Of course they are, we all are!
Time for a couple of charts. Firstly, there’s a clear distinction between performance of front line bowlers (ie. those that bowl on average more than six overs per innings) and the “change” bowlers:
Note the key difference in average between front line and backup bowlers – 12.1 runs per wicket. It’s likely that the backup bowlers bowl in the middle overs, so flattering their Economy Rates compared to the bowlers trusted to finish the innings.
Sampling the data in any way that includes a greater proportion of front line bowlers will give metrics that indicate batsmen are struggling. For instance, by only measuring performance against left arm pace bowlers!
Next, the same view as above, but with left arm pace bowlers. Note how high the average overs per innings are for left arm pace bowlers. There’s a full list of bowlers at the end of this piece.
Left arm pace bowlers average 12% less than other bowlers (admittedly while conceding runs 3% faster). For analysis of the advantages left arm pace bowlers have, refer to this Cricinfo article http://www.espncricinfo.com/magazine/content/story/851399.html
But why wouldn’t there be part-time Left arm quicks? It could be margin of error: bowling over the wicket to a right hander, straying onto the pads is risky while conservatively keeping a consistent line outside the off stump takes bowled and LBW out of the equation.
Summing up, we can draw two conclusions. When considering performance against a sub group of bowlers, one needs to adjust for the quality of that sub-group. The smaller the sub-group, the more careful you need to be. Also, expect all batsmen to average 12% less against left arm pace bowlers in ODIs.
There’s barely a part-timer in the group. Only Anderson, Franklin, Udana, Reifer averaged less than six overs per innings – and Raymon Reifer has only played two games!
Still reading? Here’s another example to make the point: imagine a naïve Cricket Analyst for a Test team at the end of last Century. Crunching the numbers they see that most batsmen underperform against leg spin, so recommend the selectors fast track a ‘leggie’. The unfortunate Analyst didn’t notice that there weren’t very many leg spinners out there. All they’ve really discovered is that it wasn’t easy to face Shane Warne, Mushtaq Ahmed or Stuart Macgill. That’s not especially insightful: right data, wrong conclusion.