If a probability function is similar to the standard normal 'bell curve', but has fatter tails, it is said to exhibit leptokurtosis, or to be leptokurtic. A distribution showing the opposite behavior, that is, a greater than normal concentration of the probability mass in the center of the distribution range, with corresponding thinner tails is said to be platykurtic, or to exhibit platykurtosis.

A useful mnemonic is to think of the fat-tailed distribution as having a strong tail, like that of a kangaroo, which is a good leaper, and is thus leptokurtic. The curve which concentrates more probability in the center has a silhouette closer to that of the platypus, and is therefore platykurtic.

sionnach commented on the word leptokurtosis

A somewhat bemused discussion of this condition, hitherto thought to have been confined to statisticians and economists, may be found here .

And since bilby is rumored to be back, the mnemonic diagram mentioned in my previous comment is below:

November 18, 2010

sionnach commented on the word leptokurtosis

If a probability function is similar to the standard normal 'bell curve', but has fatter tails, it is said to exhibit leptokurtosis, or to be leptokurtic. A distribution showing the opposite behavior, that is, a greater than normal concentration of the probability mass in the center of the distribution range, with corresponding thinner tails is said to be platykurtic, or to exhibit platykurtosis.

A useful mnemonic is to think of the fat-tailed distribution as having a strong tail, like that of a kangaroo, which is a good leaper, and is thus leptokurtic. The curve which concentrates more probability in the center has a silhouette closer to that of the platypus, and is therefore platykurtic.

April 26, 2008