Mode

The mode is one characteristic of a distribution. It is the most frequently occurring value in a group of values. The mode can be an informative description when one value occurs noticeably more often than other values. In addition, the mode is the only measure of average, or central tendency, that is appropriate for nominal (categorical) data.

For example, the age distribution in a group of 12 children is 3, 3, 4, 4, 4, 4, 4, 5, 6, 6, 7, and 8. To compute the mode, the frequency of all occurring values has to be calculated.

Value	Frequency
Age 3	2
Age 4	5
Age 5	1
Age 6	2
Age 7	1
Age 8	1

The value that occurs most frequently is a mode of the distribution. In this example, 4 is the modal age of the children. The mode tells us which age occurred more often than others.

In distributions of continuous variables, the mode can be computed as the midpoint of the histogram with the highest peak. It can be useful to revert to modal classes, sometimes called “bins” (e.g., a class of values between 1.1 and 2, 2.1 and 3), which can subsume the individual values 1.23, 1.76, 2.11, or 2.89. Note that this can cause ambiguity, because the choice of class boundaries can have a dramatic effect on the mode.

A distribution that has two peaks is called bimodal; when there are more than two peaks, it is called multimodal.

For the distribution to be bimodal, the two peaks do not necessarily have to be of equal height.

More About the Mode

• A histogram is an easy method to spot modes.
• If no value occurs more often than another in the group of values, any and every value can be considered a mode of the distribution.
• The mode is independent of the range and the shape of distribution of the represented values. Unlike the mean, it is not affected by extreme values because it does not take other values of the distribution into account. If three people had a score of 3 on a test, the mode is 3 regardless of the fact that other people's test scores ranged from 1 to 100 (because only one or two people had the same score).

Analysis Using SPSS

Figure 1 is a simple output using SPSS's descriptive feature.

Figure 1 SPSS Output