5 ms·

yeah i gave myself some grief about that aspect but ultimately decided different scales was more misleading. could go either way. also, the kurtosis of a normal

• Fomite 13y ago
  Many statistical packages (SAS IIRC) subtract 3 from the kurtosis to set a normal distribution at 0. This is an infuriating tendency.
  • madcaptenor 13y ago
    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.
• jessaustin 13y ago
  Yes, on your scale it appears that is the case. Most definitions I've seen have a -3 constant to zero out the normal, but if you say that's weird I won't argue. Incidentally, why didn't you extend the kurtosis scale to allow for a platykurtic distribution? EDIT: to the original question, I'm not suggesting the distributions should have different scales, but rather that the scale of both should be static.
  • pdog 13y ago
    It's about fat tails, which is probably why it doesn't include platykurtic distributions.