Symmetric Distributions

In a symmetric distribution it is possible to draw a vertical line through the middle so that one side of the distribution is an exact mirror image of the other.

Skewed Distributions

In a skewed distribution the scores tend to pile up toward one end of the scale and taper offer gradually at the other end.

The section where the scores taper off toward one end of a skewed distribution is called the tail of the distribution.

A skewed distribution with the tail on the right-hand side is called positively skewed because the tail points toward the positive (above-zero) end of the X-axis. If the tail points towards the left, the distribution is called negatively skewed.

Example:

Here is a Positively Skewed distribution:

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