Sunday 6 March 2016

"Martinez Blows Most Dangerous of Leads"!

Human interpretation of sporting events is often awash with cognitive biases.

It is virtually impossible to become totally free of these irrational deviations in matches where you have a vested emotional interest, but even numbers based assessments are sometimes likely to fall foul of such traps.

Many biases of this kind exist, notably, but not exclusively ranging from outcome bias, that over values the result compared to the thought process behind the original decision to recency bias, that over values newly acquired, often memorable outcomes to selection bias that limits the data to support a preconceived viewpoint.

The BBC's @philmcnulty would appear an ideal account to follow for those who prefer their information liberally dosed with irrationality.

Fresh from providing a live score service from North London, Phil was tweeting his 364k followers about Everton's soul crushing capitulation from 2-0 up at home to analytics' bete noir, West Ham.

The tweet certainly struck a chord with Everton fans who were licking fresh wounds and enthusiastically re tweeted the sentiment, along with a few dozen gloating Reds.

As if to reiterate that this was a measured appraisal of Martenez' regular inability to steer the side to their just rewards from 2-0 up, Phil later tweeted this.

So a late playing of the rationality card, "facts" were behind the initial tweet.

Since Roberto Martinez took over at Everton they have raced to 33 2-0 leads in all competitions. Of those 33 matches, Martinez has, if each game were treated as a league match, amassed a total of 90 points from a possible 99 or 91% of the possible maximum.

The only defeat I can find was yesterday against West Ham. However, prior to that they let a 2-0 lead slip when only drawing 3-3 away at Chelsea in January and had done the same at Bournemouth in late November.

So we've potentially got recency bias and selection bias lurking in the sub-conscience, especially for the emotionally attached supporter base.

If "facts" or if you prefer, a probabilistic assessment of the likely range of outcomes for a side taking a 2-0 lead in 33 matches, is more your preference, we can throw some ball park numbers at the problem to counterbalance our inbuilt biases.

Everton reached a 2-0 in these games by, on average the 45th minute. If we make average assumptions about the quality and venue in these matches, there's around a ~90% chance they win from 2-0, ~8% they draw and ~2% they lose, as they did on Saturday.

Spread over 33 games, the "facts" show that losing at least one such game from the "most dangerous of 2-0 leads" is almost as likely as not for a fairly typical mid to upper table side.

But of course, Everton weren't  a fairly typical mid/upper team yesterday. they were a ten man team from the 34 minute onwards.

A red card "costs" a side ~ 1.45 goals per game or about a whole goal from the 34th minute.

When Everton took their 2-0 in the 56th minute, but before possibly one of the league's best shot stoppers. Adrian successfully narrowed the angle for Lukaku's penalty kick five minutes later, they had around a 6% chance of losing that single game alone.

Of all their 2-0 leads, yesterday was probably the one they were most likely going to blow big time. in part due to Mirallas' theatrics. It was the least likely outcome yesterday after an hour, hence the howls of anguish, but if you accumulate enough low, but none zero probabilities over your managerial reign, sooner or later one rare event is going to bite you.

And there's no shortage of talking heads to irrationally mould possible chance into concrete character flaws.

Recency bias, outcome bias, selection bias, anchoring bias, (concentrating on one factor and ignoring all others) and opportunity bias (ignoring the number of times an outcome may have transpired).....Pretty good going for one tweet.

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