Mean, Median, and Mode
The mean is the arithmetic average of the scores. It is calculated by adding up all of the scores and dividing that total by the number of scores. The mean is the appropriate measure of central tendency when the data represent either an interval or ratio scale. Because most quantitative measurement in the social sciences uses an interval scale, the mean is the most frequently used measure of central tendency.
The median is the midpoint of a group of scores. For example, for the scores 10, 20, 30, 40, 50, the median is 30. If the number of scores is even, the median is the point halfway between the two middle scores. For example, for the scores 10, 20, 30, 40, 50, 60, the median is 35. The median is the appropriate measure of central tendency when the data represent an ordinal scale.
The mode is the score that occurs most frequently in a distribution of scores. The mode is seldom used because of the problems associated with it. For example, a set of scores may have two or more modes. Such a distribution of scores is referred to as bimodal. Another problem with the mode is that equal-sized samples randomly selected from the same target population can have different modes. Nevertheless, the mode is the appropriate measure of central tendency when the data represent a nominal scale.
