Ball Possession versus Goals Difference

I am currently doing some research on FIFA World Cup 2014 statistics and data. One relationship I investigated was ball possession versus goals difference. You might think higher ball possession equals more shots at goals equals more goals equals bigger goal difference. At least that's what I thought. But I was wrong.

The graph below shows ball possession (%) on the horizontal axis with goal difference on the vertical axis for the team with more ball possession during each game of the world cup. 

Simply put, there's no correlation between ball possession and goal difference. The data is very scattered. The best fit is quadratic with an R-squared value of 0.0272 meaning that the fit works for 2.72% of the data: useless for predicting anything.

However, the data is not completely useless. The team with the most ball possession had a negative goal difference twenty times meaning that these teams lost 20 out of 64 games (31%). A draw occurred 17 times (27%), and these teams won 27 times (42%). Note that overtime goals are excluded: only regular time is considered (includes injury time).

This is actually quite useful information. Greater ball possession means that the team has 69% chance of winning or tying a game, hence winning at least one point. They lose less than one third of the time.

The moral of the story? High ball possession won't necessarily give you a lot of goals, but it will increase your team's chance of winning the game.