Monday, 23 November 2015

Has Luck Made the Title Race Highly Competitive?

The 2015/16 Premier League has thrown up a multitude of talking points, ranging from Chelsea and Leicester swapping identities to the log jam of teams that are in competition at the top of the table after 13 matches.

Leicester entered the Premier League as above average Championship winners, so survival in 2014/15 was more likely than not, but with Premier League points sometimes coming in uneven bursts, a title contending run was required to secure safety over the final months of the season.

Despite the encouraging finish to 2014/15, optimism was hardly raised by the appointment of Claudio Ranieri, a manager better known in England for his extreme squad rotation policy than his previous tenure at the head of a title contending side.

Leicester's current position is a pleasing juxtaposition to 2014/15 when they were bottom with 10 points after 13 games compared to topping the table in 2015/16 having dropped just 11 points.

Shooting stats don't mark Leicester down as the most likely leaders of the Premier League, they've been lucky in converting chances in matches where they've not dominated in terms of volume, but they are currently a legitimately improved side from the previous season.

Leicester's 28 points after 13 matches ties with the 2010 Chelsea side as an historical low points total for a table topping team after a baker's dozen since 2000. However, points alone are a poor measure of a team's standing compared to the remainder of the league.

Currently, just four points separate the top five, compared to a nine point gap when Chelsea led the title race with 28 points after 13 games in 2010.

When measured in terms of how many standard deviations a team leading the table is above the current average points total for the league, the 2010 Chelsea team were more dominant than Leicester are despite both sides having identical records.

How Dominant were the Leaders after 13 Games.

Table Topping Team. Year Start. Standard Score.
Manchester U 2000 2.02
Liverpool 2001 2.03
Liverpool 2002 2.07
Arsenal 2003 2.12
Chelsea 2004 2.23
Chelsea 2005 2.22
Manchester U 2006 2.38
Arsenal 2007 2.96
Chelsea 2008 2.30
Chelsea 2009 2.31
Chelsea 2010 2.14
Manchester C 2011 2.12
Manchester U 2012 1.94
Arsenal 2013 1.96
Chelsea 2014 2.51
Leicester. 2015 1.51

(Teams in bold won title).

In 2015 to date, Leicester are just 1.5 standard deviations above league average, the least dominant achievement for a leader after 13 games this century by some distance. 

There are three challengers each within a win of overhauling them, including Manchester United whom they play next and it is tempting to cite the closeness of the title race and Leicester's position at the head of it, as proof that standards may be falling in the Premier League.

However, just as random variation in the matches so far may have been kind to the Foxes, it may also have compressed the higher reaches of the table compared to more recent seasons.

Instead of tracking simply points won by the leaders in shot based simulations of the current table, we can partly estimate how competitive each iteration was by calculating the distribution of standard scores for each table topping team.

Slightly more than 10% of season simulations for 2015/16 give a leader who is less dominant than Leicester are to date. The most likely outcome produces a leader that is between 1.8 and 1.9 standard deviations above average and 22% of simulated leaders have standard scores of 2.0 or above.

Random variation may possibly have propelled Leicester to the head of the Premier League. It may also be responsible for making the current table appear more competitive than it may actually be.

A single anomalous batch of 130 matches is far too early to call time on the title regulars, induct new members or declare a new found equality in the higher reaches of the table, 

Saturday, 21 November 2015

Everyone Loves Ricky.

Everyone loves an individual goal. Be it Peter Beagrie beating six players (or the same player six times) in the late 80's to John Barnes in the Maracana and Ricky Villa lighting up the old Wembley Stadium.

It may be a trick of the mind, but such unassisted goals also seem to have an air of inevitability. Once the last line of defence is reached the keeper rarely spoils the party.

There may be legitimate reason for this impression. A player who has largely created his own chance has often disrupted any defensive organisation that had previously existed, while being fully in control of the ball, rather than stretching to master an over hit assist.

While imperfect, the absence of an assist in an attempt description might serve to identify goals or shots that were a result of individual skills, rather than a chance created through a series of team based passes.

Using a season's worth of shot data from open play, it does appear that unassisted goal attempts result in scores at a higher rate than attempts originating from an assist. This may have occurred by chance, but the analysis strongly suggests otherwise.

A Spurs legend dreams of historical deeds.
As a baseline figure using single season data, once location is accounted for, an unassisted on goal attempt is around 10% more likely to be scored than an attempt that came about by a teammate setting up the chance.

This has implications for both teams and players who may be adept at creating potentially better quality chances through individual effort compared to relying more on a teamwork based approach, where the opposition may be able to defend more cohesively.

In 2012/13 only 15% of Arsenal's on goal attempts from open play were lone wolf attempts compared to 25% for Sunderland. However, variation of percentages should be expected, even if all teams have broadly the same propensity to create individually crafted chances.

Premier League attacks, based on the limited data I have, do created widely different numbers of chances from open play, (Arsenal created almost twice the number for Sunderland) and within these chances are varying proportions of individually created chances.

However, the spread in 2012/13 was insufficient to conclude that Sunderland's higher proportion of individually created chances compared to say Arsenal, is a real trait that may persist. It could be, but more data is needed.

The same could not be said for Premier League defences in 2012/13. The league average was for 20% of open play chances faced to be predominately the product of an individuals efforts. But this fell to 9% for Reading's defence to a high of 29 for Arsenal.

This time the spread could not be explained away as merely random variation. At the very least for that season, opponents seemed to be attacking certain sides in a variety of biased approaches from open play.

The quantity of chances faced will always overwhelm any persistent bias in the type of chance allowed, but identifying if and perhaps why a side is allowing a larger percentage of individually created chances, that may carry a greater sting in the tail, may make for marginal gains.

Also individuals, who aren't called Messi or Ronaldo, may be unfairly define as having a lucky season, when they are actually rather good at persistently emulating Ricardo Julio Villa.

Thursday, 19 November 2015

Bad Mood.

On Tuesday night I won the lottery. OK not really, but I was involved in an extremely low probability occurrence.

To briefly describe the event. We were going to see The Vaccines at Wolves Civic Hall, an indie rock band from West London with a fan base that is almost exclusively young. So our mere presence as a very small right hand tail of the audience age distribution was unlikely in itself.

The route, car used and departure time was dependent on a multitude of random decisions, chosen arbitrarily on the night.

How long it took to bribe the cat with extra food, which routes to take to avoid the traffic chaos that is currently Stafford town centre, how many cars to overtake, when safe and legal to do so and how many cars to let out from side roads.

Not my fault.
An hour after a journey that usually takes an hour in total we were still crawling through Stafford when the remnants of hurricane Barney deposited a six foot long tree branch onto the roof of my 2003 mini bought new on the same day England won the Rugby World Cup..

There were no injuries, the car was driveable, but a total write off.

No other car I saw that night was driving around with recent storm damage and none of the drivers appeared particularly adept at dodging unseen projectiles. So I concluded that I'd been unlucky in the extreme. (although when you emerge unscathed from such incidents, you're invariably told how lucky you've been).

The chances that I was going to be on the wrong end of a tree branch on Monday prior to the event was very, very tiny.

Improbable, but not impossible and the same was true for everyone else on the road. But so many drivers were around that night across the path of Barney, each with a very small chance of getting written off that the chance that someone was going to suffer that fate was significant.

I was just the "lucky" one.

1 chance in 20 is often taken as the arbitrary measure of when something unseen is thought to be at play, such as talent to avoid flying trees or to score more goals than expected.

But unless there is corroborative evidence to back up the claim that an event is the product of additional skill and luck, it is worth seeing how many players are "on the road" in case you are simply seeing a notable and unlikely event that was almost bound to happen by chance to one of a numerous group of similarly talented individuals.