There are some good reasons for this. For example, if Y is the sum of n independ...

madcaptenor on July 2, 2013 | parent | context | favorite | on: Normal vs. Fat-tailed Distributions

There are some good reasons for this. For example, if Y is the sum of n independent and identically distributed random variables with the distribution of X, then the kurtosis of Y is 1/n times the kurtosis of X. This doesn't hold without subtracting 3.