Skew

The 'skew' of a dataset indicates how much the distribution of the values in the variable differs from a symmetric distribution. A symmetric distribution (such as the normal distribution) can be divided into two parts by a vertical line drawn through the mean...which is also the median and the mode. By contrast, skewed data has different values for the mean and the median. The histogram here is of gasoline prices and shows some skew to the right. Try this yourself with the "Gasoline" datatset.

We can see that there are some high gas prices which 'drag' the data to the right. So we would expect the mean to be larger than the median. Which it is: mean is 234.96, median is 234.25. The difference is small and also by eye we can see that the skew isn't much. As a result the figure for 'Skewness' given in the Descriptive Statistics is only 0.07993. Note that this is a positive number, indicating a skew to the right (where the tail is). A negative skew is the same thing, but in reverse.