Should you go for bull last dart in hand from 121?

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December 23, 2015 by bsd987

This is one of the questions I’ve had: Is it correct to go for bull last dart in hand from 121? Numerous top professionals—Barney and Mensur Suljovic for instance—will almost always go for bull from 121 last dart in hand. Getting down to the two-dart 96 or hopefully 71 is better than the risk of leaving 101 and having to use all three darts. But the numbers so far at least raise questions as to whether this is good strategy, at least so long as the T20 bed isn’t blocked.

I’ve talked in the last blog post about checkout percentages for different types of combinations. I will now post the cumulative data that I have from nine sessions for all checkouts of less than 120.

Combination Made Attempts %
Double 262 359 72.98050139
Odd (e.g., 25)/41-61, 65 108 166 65.06024096
62-64, 66-80 68 139 48.92086331
81-98, 100 36 149 24.16107383
99, 101-120 31 170 18.23529412

As expected, the more complex the checkout, the less likely it is to be hit. But look at how little the improvement is from 101 to 96: You go from a slightly less than 1/5 shot to a slightly less than 1/4 shot. You do improve your chances of hitting by about 32%, but you improve a very low chance to a slightly less low chance. If you hit the bull—which so far is a 31% proposition—you leave 71, and have improved to nearly a 1/2 shot. But 70% of the time, you’ve made only a slight improvement.

Now, I have not studied treble hitting this tournament. But I can make an educated guess as to how often a top pro hits a treble he’s aiming at. In order to average 94—which comes to 16 darts a leg—a pro with a slightly above average 40% on the doubles will average a bit better than 40% on the trebles. We will for simplicities sake assume on the low end (and thus more favourable to going bull) and say he hits exactly 40% of his trebles. At 40%, in an average leg without spraying any darts, he’ll be down to 141 after 10 darts. Assuming a S20 with the next, that gets us to our 121 last dart in hand. When the 20 bed is not blocked, he will have a 40% chance of leaving 61 and a 60% chance of leaving 101. Using our tournament-to-date statistics and simple multiplication, the chances of going out from 121 in 4 darts if you go for T20 are 34.09%. If you have to switch to T19, it goes down to 27.64%.

Let’s compare going for bull and making the pro-bull assumption that a top pro will not miss at least the outer bull and that the bull percentage on checkouts equals the overall bull hitting percentage. Taking that double bulls are hit around 31% and multiplying accordingly, we get 32.0014% chance of going out in 4 darts if you aim for bull. But that is with every statistical assumption in favour of going for bull. If we assume that 1/10 times a player misses the bull entirely, we are down to 31.41%. If the bull hit percentage actually goes down to 25%, we’re down to 29.76%.

The numbers are so close and the attempts at bull so few that so far I can’t criticize a player either way. I will re-evaluate the data at the end of the tournament. However, it does seem that barring the first nine sessions being well out of whack from the norm, if the T20 bed is blocked, going bull is the correct modus operandi. When we took all the pro-bull assumptions out of the calculus and tried to turn them into anti-bull assumptions, it still kept the checkout rate higher for going for bull than for going for T19.

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