Descriptive statistics often involves using a
few numbers to summarize a distribution. One important aspect
of a distribution is where its center is located. Measures
of central tendency are discussed first.
A second aspect of a distribution is how spread out it is. In
other words, how much the numbers in the distribution vary from
one another. The second section describes measures
of variability. Distributions can differ in shape. Some distributions
are symmetric whereas others have long tails in just one direction.
The third section describes measures of the shape of distributions.
The final two sections concern (1) how transformations
affect measures summarizing distributions and (2) the variance
sum law,
an important relationship involving a measure of variability.