When we hear that it takes an average of ten thousand hours to become an expert in most fields, we should ask what is the standard deviation around that average? One way to think about an average is that it is a single number that describes a set of results. The standard deviation tells us how well an average characterizes a set of data. If the standard deviation is zero, then all values equal the average and the average gives us perfect information. As the size of the standard deviation grows the average becomes less informative.

How good is the ten thousand hour average?:

“However, recent research has demonstrated that deliberate practice, while undeniably important, is only one piece of the expertise puzzle—and not necessarily the biggest piece. In the first study to convincingly make this point, the cognitive psychologists Fernand Gobet and Guillermo Campitelli found that chess players differed greatly in the amount of deliberate practice they needed to reach a given skill level in chess. For example, the number of hours of deliberate practice to first reach “master” status (a very high level of skill) ranged from 728 hours to 16,120 hours. This means that one player needed 22 times more deliberate practice than another player to become a master. “

As we can see from the video below, the ten thousand hour rule is very much alive in the popular mind: