Penalty Kicks and Saves

In the spirit of the World Cup:


For most professional soccer games, the average number of goals scored is around 2.5 a game so penalty kicks, with their high success rate, are crucial to the game's outcome.

 

Research headed by Michael Bar-Eli at the Ben-Gurion University of the Negev in Israel makes some interesting conclusions about how goal keepers should defend penalty kicks.
They analyzed hundreds of penalty kicks over a season, including only shots on goal. (Importantly they left out missed shots, which has some implication to their results.) 85% of the penalty shots placed on goal were successful. A bit more than half of the shots taken were placed in the lower one-third of the goal (57%). These low attempts were successful about 80% of the time. By comparison, only 13% of shots were placed in the upper third of the goal. However, all of these shots resulted in a goal scored (100% success).
Slightly more shots were placed to the goal keeper’s right side compared to the center or left. (The handedness of the shooter was not compiled.) Of these three directions, kickers were most successful when shooting at the center of the goal. Shots aimed at the center of the goal were successful 87% of the time compared to an 83% success rate for shots placed at the outer thirds of the goal. (Again, only shots on goal were analyzed; missed shots were not included.)

Professional penalty kick shooters most often place the ball at the lower right corner of the goal (40% of attempts). However, they are far more successful when shooting at the upper portion.(But I'll bet they miss more often there.)
In attempting to stop the penalty kick, goal keepers jump to the right or left 94% of the time. In doing this, they guess correctly only about 40% of the time (i.e. jump left, shot placed left). However, even when they guess correctly, they only stop 25-30% of the shots. The most intriguing part of the Dr. Bar-Eli’s analyses is that when goal keepers remain in the center of the goal and the shot is placed in the center, they make the save 60% of the time. Given that about 30% of penalty kicks are placed in the center third of the goal, remaining stationary in the center of the goal increases the keepers chances of stopping the shot from about 13% to more than 33%.

So why does the goalie move?

Interviews with goalies show their decision is based on the perceived need to “do something” rather than nothing. In sports, perhaps mistakes are more forgivable if they are made at full speed. Diving to the left or right gives the appearance of effort and avoids the perception that he/or she didn’t attempt to make a save. In fact, a survey of goal keepers show that the vast majority feel worse if a goal is scored when they remain central versus diving to the left or right.

The invariable comparison to life and business occurs here. (For example, the success of "robot trading" might be the elimination of such an "action bias.")

Despite the need to make a heroic effort, some situations may require doing less rather than more.