SKEWNESS

The third momentabout the meanis relatedto the asymmetryor skewnessof a

distribution:

m₃=

n

Aunimodal(i.e. a singlepeaked)distributionwith µ₃< 0 is said to be skewed to

the left -- that is, it has a left "tail".If µ₃> 0, the distributionis skewed to the

right.For symmetricdistributionµ₃= 0

=

Skewness=

s

The quantity measuresthe skewnessof the distributionrelativeto its degreeof

spread.

This standardizationallows us to comparethe symmetryof two

distributionswhosescalesof measurementdiffer.