Some Problems With Stats

As an avid follower of all things statistics it is great to see all the soccer blogs popping up analysing data. This has been made possible in a large way by the data released my Manchester City. What is great to see is the wide range of analysis and critiquing done by the community. In most cases this community operates outside the game i.e. they are not Performance Analysts working within clubs. This allows them a certain amount of freedom to publish things that clubs might consider sensitive information.

I think we have barely even started this process in GAA. There are only a handful of bloggers/journalists using data on a semi-regular basis. For many reasons the evolution has been a bit slow but I wanted to make a couple of points.

1. Averages;

while averages can be very useful they should come with a bit of a warning. I have recently finished a project looking at the the effects the quality of the opposition can have on performance. It was found to be significant. This basically means that when calculating averages I account for the quality of the opposition. I create 1 average for ‘Top Teams’ and 1 for ‘Bottom Teams’ – combining the 2 masks the ‘real’ performance. We can now benchmark our performance not just against the overall average but against a more specific one. Averages alone might mask the true performance.

2. Context;

I will be the first to admit that stats will never tell the whole story. A lot of the time you need to look at video. It can be very difficult to get stats to give you all the context you need – but that doesn’t mean you shouldn’t try. For Example: If you are looking at shooting averages – comparing them to the Championship average is a great start but there are other factors you need to consider.

  • Game Situation: Is a score when you are behind by 1 worth much more than when you are ahead by 10? I would think so and therefor needs to be considered.
  • Game Time: The stage the match is in might also be important (First minute v’s Last Minute). Coupled with the game situation above, scores at different times in the game might also need to be considered.
  • Shot Location: Where on the pitch a player scores from is also important when comparing performances. Inside/Outside the scoring zone for example.
  • Opposition Quality. Against opponents of different quality you will get different results. You need to factor this into any performance % you measure.

3. Sample Size

GAA teams play an extremely small amount of competitive games. For example in last years championship there were 61 games. That’s across 33 teams. Donegal played only 7 games. In contrast Man Utd played 38 games in the EPL alone add on the FA Cup, League Cup and Champions League and you get close to 61 games for them alone. This sample size makes it easier to draw real conclusions from the data. It’s never going to be like this in GAA so we need to work with what we have got – but is worth keeping in mind and we need to be mindful of making statements based on small sample sizes.


Is Football Getting Less Competitive?

There has been much talk over the last few weeks about the one-sided nature of some of the games we have seen this year. Rather than just accept this as a common view – lets look at some real data. (Data from 1/5/11 – 26/6/11 — 1/5/12 – 26/6/12)

Total Points Scored

This first graph shows the Total Points scored (on average) for the 2011 and 2012 season. It’s broken down by province.

The only province seeing less points per game is Munster – which could be explained by Kerry & Cork meeting earlier this year than last year. But Munster aside all other provinces are seeing an increase in total points scored. Despite the perception of blanket defenses ruining the game we are in fact seeing an increase in points scored!!


Perhaps more important than the total scores in a game is how competitive the games have been. The simplest way to measure this is to look at the points difference between winning and losing teams. The graph below shows the picture of this based on the same data as above.

An increase in these figures means the games are less competitive. All but Connacht are showing signs of more competitive football. So despite the perception, caused by some very one sided games, when we look at the overall picture football is as competitive as last year.

This figures might change over the course of the season but comparing this year with the same period last year we can see that total points per game are up and game competitiveness is improving.


Gaelic Football World Rankings

The First Unofficial Gaelic Football World Ranking

World ranking is well documented in other sports. I wanted to see if it would be possible to do the same in Gaelic Football. I examined the methods used by Soccer and Rugby and stuck very much to those lines. Once you have the match results data and a formula to follow its an easy enough process.

The Formula:

Result Points: This is quite simple the winning team is awarded 3 points the losing team 0 and if the match is a draw 1 point is awarded to each team.

Match Status: This can be argued back and forth (and no doubt will), but I needed to assign a match importance weighting. The ranking was as follows;

  • Championship Game: 4
  • Qualifier: 3
  • League: 2

Opp Strength: This was by far the hardest to calculate. First I needed a starting ranking I took the league tables from the 2008 season and ranked teams in the order they finished 1 – 33 (rather arbitrary – but as you will see historical results have less of a weighting). I would obviously have preferred to use Championship games but it is very difficult to rank teams in the championship.

That got me my ranking for the start of the 2009 season. Once I calculated a World Ranking based on the method below I used that on going.

Historical Weighting: Again I copied FIFA here, they assign different weightings to games depending on how long in the past they happened. (2009 = 0.2, 2010 = 0.3, 2011 = 0.5, 2012 = 1). Therefore games that happened in 2009 are not as important as games played in 2012.

Ranking Points = 100(Result Points x Match Status x Opp Strength x Historical Weighting)

This is averaged for the 3 years involved (will be 4 years when I add 2012). So here is the current standings as at Jan 1st 2012.

Team Ranking
Dublin 1
Kerry 2
Cork 3
Kildare 4
Donegal 5
Tyrone 6
Down 7
Mayo 8
Roscommon 9
Wexford 10
Limerick 11
Meath 12
Derry 13
Armagh 14
Wicklow 15
Laois 16
Louth 17
Offaly 18
Antrim 19
Longford 20
Sligo 21
Waterford 22
Leitrim 23
Cavan 24
Carlow 25
Tipperary 26
Monaghan 27
Clare 28
Fermanagh 29
Galway 30
Westmeath 31
London 32
New York 33
Kilkenny 34

No doubt there are many talking points in both the tables and the method I have used. Perhaps the league should be less valuable or provincial championships weighted differently than the All Ireland Series. If you have any thoughts on ways to improve this please let me know. I would love to get your thoughts.

All Ireland Final’s – A 100 Year Visualization

I have been playing around with different ways to visualize data. This is a table I have put together for all the All Ireland Final Results since 1911.

Here is a quick guide to what you are looking at.

Left Axis: Winners Total Score
Bottom Axis: Year
Colour: Province
Bubble Size: Margin of Win
Team: Winner

If you hover over the bubble you will get more information such as the runner-up.


Love to get your thoughts on this and maybe any suggestion on how it might be improved.

Moneyball & Gaelic Football

What has Moneyball got to do with Gaelic Football?

For those who don’t know, Moneyball started life as a book about Baseball but in reality it has become much more than that. Now a Hollywood movie with the lead character played by Brad Pitt, essentially it is a story of how an underdog team – The Oakland A’s – used statistics to recruit players that all the other ‘big’ teams undervalued.

As the Moneyball movement spreads across the Atlantic it has caused somewhat of a revolution in sports analytics. But there is a problem – coaches, managers and some in the media just want to dismiss the use of statistics in ‘their’ game as nonsense. ‘Stats have no place in Gaelic Football’ is a common statement I hear.

Are the right?

Well… yes and no. The wrong stats will always be wrong. For example on Newstalk radio at the weekend there was a conversation on this topic. One stat that was thrown out was; Kieran McGeeney in the All Ireland Final and how he was taken off because he hadn’t touched the ball in 18 minutes. People are only too happy to use stats like this to make a point of how stats have no place in football.

This stat will never have any use in football – so what he hadn’t touched the ball? It’s the wrong stat to look at. If this is an example of how stats have no place in football then you are right. But my point is that it’s not the right thing to look at – it’s just a bit of information. There is absolutely no context applied to this. Coaches and managers using this information have to apply some game knowledge to interpret this information.

For example

  • Did his man touch the ball in that 18 minutes?
  • How much possession did Armagh have in that 18 minutes?
  • How many possessions do you expect him to get?
  • Does he need to have possession for Armagh to win?
  • Does taking him off have a psychological affect on the team or opposition?

These are all elemnts that would need to applied to this tiny bit of information before it becomes in anyway useful.

Moneyball is a book about Baseball, a fairly static sport compared to Football. When it boils down to it Baseball is a contest between two players the pitcher and the hitter. Football is a contest between 15 – 20 players, with a whole host of tactics thrown in.

So as somebody who collects and analyses ‘the numbers’ in Gaelic Games, this might seem like a strange thing to write. Do I think sports analytically can be applied to football & hurling? Absolutely – but we must look at the right stats not just ones that are easy to collect or that make a great headline in the papers. There are stats that managers up and down the country are placing too much emphasis on (Kickouts) and there are important stats they are ignoring (Turnovers), to give just two examples.

Stats have a place in all sports, my point is that if we always look at the wrong stats they will always be wrong. I am only starting my journey collecting stats in Football & Hurling and who know’s what we might discover. As teams constantly look for that 1 or 2% to take them over the line who can say we won’t find some value in examining the numbers?

Ball in Play Worry for GAA

Ball in Play Worry for GAA – Rob Carroll

The following article appeared in the Irish Independent on Tuesday. If you are interested in learning more about the stats mentioned in the article or about the analysis service we offer please get in touch.

By Colm Keys

Tuesday October 11 2011

The ball was in play for an average of 34 minutes and 38 seconds per-match during this year’s GAA football championships, it has emerged.

Statistics compiled by performance analyst Robert Carroll show that Gaelic football championship matches enjoyed just 46pc of action — inclusive of added-time — in this summer’s championship.

Carroll took his information from the 29 games televised live over the summer and concluded that the figure is considerably lower than the AFL average, which is 60pc.

‘Ball-in-play’ does not include the time between when a foul is committed and when play resumes or when the ball goes outside the pitch parameters, according to Carroll.

The most action, as defined by Carroll, was seen in theLeinster football final between Dublin and Wexford in July, when the ball remained in play for 41 minutes and 55 seconds. This was the only game where the 40-minute barrier was passed.

The smallest amount of actual playing time was recorded in the Ulster quarter-final between Tyrone and Monaghan, which had just 30 minutes and 39 seconds of action.

“A 46pc figure would be low by comparison to other sports,” said Carroll. “The AFL is now 60pc and has probably jumped 10pc over the last decade.”

Carroll, from Toca Sports, pointed out that there were 21 more shots at goal in the Dublin’s clash with Wexford than there were in the Tyrone and Monaghan game.

“From looking at these games it becomes apparent how persistent fouling is interrupting games,” said Carroll. “That is the biggest time-killer.”

One of the highest figures of ‘ball in play’ (38.41) was recorded in the Connacht semi-final between Roscommon and Leitrim in Carrick-on-Shannon, on one of the wettest championship Sundays.

Carroll is hoping to provide a database of such statistics in the coming years which may provide an insight into the changing trends in Gaelic football.

– Colm Keys

Irish Independent