Sunday 9 March 2014

Jonathan Walters Penalty Watch.

Stoke's Jonathan Walters could probably do with a bit of a lift this morning. Fresh from being branded the poster boy for terrible Premiership penalty takers following his two own goals and penalty failure against Chelsea and an opening day miss at Liverpool, he has just converted two spot kicks in a week.

The first, low to the keeper's *** defeated Arsenal and yesterday, high to the keeper's ***, he earned a point at Norwich. Particularly satisfying for a former Ipswich player. Unfortunately, he then fell into the on going Stoke narrative by getting sent off with a straight red card five minutes later, without even being able to plead lack of intent to a sympathetic official. Shrugs, rather than smiles all round, unlike at the Hawthorns in the early kick off.

There are bigger bogeymen in Stoke's current team for Walters to jump to the head the hatchetman hate list, but he still merits a page one entry on Google when you search for the Premiership's worst penalty taker. The seeds were sown by Eurosport's use of small sample sized efficiency rates to compile a list of penalty taking shame. A route also trodden by the Telegraph following the Irish international's mishaps against Chelsea. The stats, apparently don't lie, although they do invite writers to make a cast iron case based around numbers that are awash with randomness.

Adam & Walters. a godsend for lazy journalism.
In this post I looked at how often a player with a league average conversion rate of around 78% would score from 8 or fewer goals out of 13 penalty kicks, Walters' record after the Mignolet save. If you lined up entirely average Premiership kickers and keepers, around one in ten average penalty takers would post a record at least as bad as Walters had up to 3 o'clock on opening day after 13 tries.

So rather than "the stats not lying" as the unnamed Telegraph hack suggested, they can only really be used to couch opinion in terms of probabilities and likelihood. Outcomes are a product of both randomness and talent and not simply the latter. (note to the Telegraph, Walters isn't a defender, either, although this is a more forgivable mistake to make if your were only a casual observer of Stoke under Pulis).

Two further penalties down the line, Walters now has a 10/15 (67%) record or 12/17 (71%) if you include one FA Cup penalty and one League Cup shootout success as a Stoke player. If you now simulate an average penalty taker attempting 15 penalties, we can see how often such a player would score with 10 or fewer  of his kicks.

There is now very nearly a 25% chance that an average penalty taker will fare as well or worse than the 10/15 record currently owned by Jon Walters and now if we line up our parade of average shooters around one in four will only just make it into double figures from 15 attempts.

Efficiency figures or success rates are a perfectly acceptable way of expressing what has actually happened, such as when a team is out shot, but sneaks the only goal of the game with one of their few efforts. But it becomes a step too far when, these limited pieces of information are used to support entertaining, but fundamentally flawed narrative.

Walters is a professional footballer, playing in one of the top leagues, as well as being a full and experienced international player, (for whom he's scored a spot kick). So it is likely that his penalty taking talent is going to lie around the fat, middle of the distribution, despite any needs of a quick fix narrative based on barely a dozen or so trials.

He's most probably neither a king or a pauper.

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