Central tendency refers to the middle of a data set or where the scores in a data set tend to fall. There are three measures of central tendency; these tell us the average score (mean), the middle of the score range (median), and the most frequent score (mode). Together, these measures provide a good overall snapshot of the data.
However, some measures of central tendency are better to use than others depending on the spread of a particular data set. For data values that are clustered around the center of the possible score range, the mean is the best representation of the data. For values that are clustered around one end of the data range, with outliers falling on the other end, the median gives a better picture of the data. For this reason, typical family income in the U.S. and many other countries is presented as a median rather than a mean.