Measures of central tendency summarize a whole data set by describing its center, or typical value, rather than just its highest and lowest scores.
When there are no extreme scores, the mean is usually the best choice because it is built from the actual value of every score.
A single extreme outlier can drag the mean far off track while the median barely moves, so researchers usually favor the median when outliers are present.
The mode is most useful when you specifically need to know the most common response.
Key terms
measures of central tendency
Statistics (mean, median, and mode) that describe the center, or typical value, of a data set.
mean
The average: add all the scores together and divide by the number of scores.
median
The middle value when scores are put in order from smallest to largest.
mode
The value that occurs most often in a data set.
outlier
An extreme score far from the rest of the data, which can pull the mean off track.
Watch out
One extreme outlier can pull the mean far off while barely moving the median.