Sunday, February 27, 2011

Analytics and Cricket - V: Death by Forecast

Is cricket the only sport in the world where a game-changing decision, i.e., an "out" is decided by a forecast? Welcome to the "leg before wicket" rule. Here, the umpire (aka the referee in the USA) gives the batsman out if he deems that the ball would have gone on to hit the stumps if the pad had not come in the way. A good percentage of outs in cricket occur via the LBW. There is some additional 'fine print' that must be satisfied in addition to the above requirement for a batsman to be given out and too technical for this tab. Here's a clip of Pakistan's great pacer Waqar Younis getting some LBWs with his fast (90-95mph+) in swinging (curve ball) yorkers in the early 1990s.

The LBW rule is unique in that a batsman is given out based on something that did not actually occur, but would have probably occurred. Not surprisingly, LBWs are the most contentious decisions in cricket. Yesterday's sensational world-cup match between India and England in my home town that ended in a dramatic last-ball tie included an LBW incident. The 2011 cricket world cup allows the use of the "Hawk-eye" trajectory predictor to help arrive at the best decision. Similar technology is used in many other sports now such as tennis. In yesterday's instance, a batsman was deemed "not out", overruling Hawk-eye's prediction, since he was struck on his pads, which was more than 2.5 metres in front of the stumps at the time of impact, a 'magic number' threshold beyond which, the Hawk-eye forecast is deemed practically unreliable. I believe that this is just the start of the problem.

Spin bowling. How the heck is Hawk-eye going to predict the amount of spin (turn) off the pitch ?? In more complex cases, there is drift, dip, as well as turn. Watch the Aussie legend Shane Warne bowl this incredible "ball of the century" some 17 years ago. Would Hawk-eye have been able to accurately predict the path of the ball after making contact with the surface of the cricket pitch ?? I some how doubt it.

Strictly speaking, forecast-based decisions do exist in other sports as well. In basketball, we have goal tends that are probabilistic calls in the sense that the scoreboard is updated based on a forecast rather than an actual basket. Are there other popular sports where non-trivial game-time decisions involve a forecast of some kind ?

In cricket, the forecasting story just doesn't stop there. We have forecast-based rules for weather-affected matches that were devised by OR professors in England - something which we already talked about before. These are causal predictive models employed regularly in professional cricket. Yet another reason why cricket is called the 'game of glorious uncertainties", and why the game of cricket is always an applied-mathematician's delight.

Given that this is world-cup cricket time, the next post will (probably) center around cricket, and will focus on a very deterministic analytical modeling element. Go India ...


  1. In baseball, the infield fly rule ( results in an out before the ball even comes down. Also, errors are awarded (or not) based on forecasts that an out would (or would not) have occurred had the ball been played "correctly".

    Must be something about sports where people smack balls with sticks. I wonder if golf also uses forecasts? :-)

  2. There is much more (out and out quantitative) forecasting based decision making going on in Cricket ODIs since 1997: The Duckworth-Lewis rule forecasts how much a team batting second would have scored given the number of balls left and wickets down in case of rain, and whole matches are won and lost because of those forecasts.


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