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Is it essential to be drawn low in the Betway Chester Cup?

05 May | BY Betway | MIN READ TIME |
Is it essential to be drawn low in the Betway Chester Cup?

By James Willoughby

THE Betway Chester Cup is nearly 200 years old and firmly established as one of British racing’s best-loved handicaps. A key element for punters is the effect of the draw: horses from low-numbered stalls usually cover less ground in a race where every inch can be important.

However, in a full field of 17 nowadays (formerly, the safety limit was higher), going the shortest way round inevitably means encountering the highest concentration of rivals; so, there is an increased chance of trouble-in-running for hold-up horses. And even for those up front and out of trouble, getting an inside pitch often involves running hard early; if too many jockeys have the same idea, an overly strong gallop can be destructive for those too intent on saving ground.

To conduct any thorough statistical analysis, we need to define clearly the proposition, or ‘hypothesis’, we want to investigate.  In this case, the hypothesis is “the betting market tends to put too much emphasis on the draw in the Chester Cup”.

Let’s start by investigating whether the draw actually influences the result of the Cup at all. The naïve approach is to use so-called ‘counting stats’ – merely the aggregating of the winning stalls. Our data set is going to be the 18 renewals since 1997. Figure 1 displays these results in the form of a bar chart:

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 Figure 1: the stall number of the winning horse in the Chester Cup since 1997

It appears that Figure 1 tells its own story: the winners seem to have come mostly from low-numbered stalls which are towards the inside of the course.

To underline this conclusion, let’s bucket the stalls into thirds (stalls 1-6; 7-12; and 13 and higher) which are labelled ‘low’, ‘middle’ and ‘high’ in the infographic which is Figure 2:

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Figure 2: Chester Cup winners since 1997 from each third of the draw

 Okay, so this appears pretty straightforward: as expected, a low-numbered stall is an advantage, at least according to the location of past winners. Unfortunately, while this level of analysis is often considered conclusive in racing, it is nowhere near solid enough to satisfy anyone who really knows what they are doing in statistics.

What’s missing is the concept of statistical significance.  So establish this, we need to compare the observed results with random chance. The apposite question is: given the probability that the Chester Cup winner comes from the lowest third of the draw is 0.33, what is the chance of finding at least 11 such winners in a sample of 18, as above?

The result, using a probability theory called the binomial distribution, is 0.003566 or 0.36%. There is only a 0.36% (332-1) chance that Figure 2 is just an artefact of randomness.

This, then, is apparently sufficient mathematical proof of the widely-held assumption that low numbers have held an advantage in the Chester Cup since 1997. Or, is it? In conducting what is referred to in probability as an ‘experiment’, we have failed to control for a potentially important factor:  the preponderance of winners among the low numbers could have just happened because most of the favourites happened to be drawn there.

Read further Willoughby analysis of the effect of the draw on the Betway Chester Cup here

 

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