Numbers Stuff: Using Rolling Batting Averages To Look At Form

Here at 51allout we love all things cricket, despite the best efforts of Amjad's front foot and the weather at Lord's. But one thing we particularly love are the numbers. Cricket has always been a numbers game and Sky (et al) do a decent job of bringing these to life. But we can do a whole lot better than that...


Number Two: Using Rolling Batting Averages To Look At Form

The idea of using a player's batting average to determine how good they were at the crease is a pretty fundamental one. And in general, it makes a lot of sense, particularly when looking back at an entire career. Across a large number of innings the balance of good and bad luck should have evened out, so a player usually ends up pretty much where they deserve to be in the greater scheme of things.

But while the destination is one thing, we're far more interested in the journey.

In order to compare a player's form against their overall career record, we can use the idea of a rolling batting average. Here we take the players last x number of innings and calculate their average, exactly as we would for their career overall. We can then track this rolling average throughout their career, to see the peaks and troughs.

For the sake of this analysis we've taken x to be ten, so that we consider the last ten visits to the crease for each player. Why ten? There are a few reasons but the main one is that this represents a 'reasonable' length of time. One or two bad innings alone won't necessarily drag it down while one big innings won't inflate it excessively. It would also represent a full five test series in theory, but that's wishful thinking these days.

As with all these things, it's easier to work through an example so we'll get straight into it. Here we're looking at the Test career of Michael Vaughan (career batting average 41.44, which is decent, but not great).



In order to make it easier to follow, it's broken up into years by the green lines. Note that there's no 2006, due to Vaughan's knee problems.

The blue line is Vaughan's cumulative career average. So after ten innings (at the start of the chart) it was 27.8. After 147 innings it was 41.44 (the end of the chart). It actually peaked at around 51.57, somewhere around the start of 2003.

Now the red line is Vaughan's rolling ten innings average. This tells us lots about how he ended up with his final numbers. Towards the end of 2002 his rolling average is up around 100 - this is due to some serious scores against India (100, 197 and 195) and his first hundred vs. Australia (177).

After this peak, however, it's a series of ups and downs. The rolling average makes a few excursions above 50 and a few below 30 and is seriously tailing off from 2007 onwards. It's this patchy form from 2003 onwards that saw Vaughan drop from a top-drawer average (above 50) to a reasonable one (above 40), i.e. the short term form drags the career average down. It's no coincidence that this was the also the period when he captained the side.

Let's consider another example now: Paul Collingwood (career batting average 40.56)



Even though Collingwood ended up with a very similar average to Vaughan there aren't the same peaks - his rolling average touches 70 a couple of times - and the low is much lower, with his rolling average just 11 at the end of his career. In between though, there isn't quite the same up and down variation that Michael Vaughan had i.e. Collingwood was more likely to scratch around for a few runs, rather than get out cheaply.


While it's quite tempting to fill the internet up by doing these charts for everyone who's ever batted ten times in Test Cricket, it's probably not the best use of a bank holiday. Instead, there's another step of analysis from this, that we'll save for a blog post in the not too distant future...