Tabulation applications allow the inclusion of summary statistics in the tables. Available statistics include Mean, Mode, Median, Minimum value, Maximum value, Standard Deviation, and Variance, as well as Percentiles (N-tiles). Most of these give information about the distribution of values for the data item. These do not make sense for some items so you should only use them if you have some understanding of their meaning and purpose. For example, none of these measures have any meaning for an item such as sex.
Mean, Mode and Median are measures of central tendency. These are measures of the location of the middle or the center of a distribution. The definition of "middle" or "center" is purposely left somewhat vague so that the term "central tendency" can refer to a wide variety of measures. The mean is the most commonly used measure of central tendency. Mean is the average value of the item, mode is the most common value occurring in the data, and median is the middle value (half of the values occur above this value and half below, e.g., 50th percentile).
Minimum and Maximum are the lowest values and highest values, respectively, found for the data item.
Standard deviation is a statistic that tells you how tightly all the various values are clustered around the mean in a set of data. This measure is the square root of the variance.
Variance is a measure of how spread out a distribution is. It is computed as the average squared deviation of each number from its mean.
N-tiles are values that divide the data values into N groups, each of which contain 1/N of the values. If N is two, then this measure is equivalent to a median.
See Also: Tally Attributes for a Variable