The LessonThe mode is an average of a set of numbers. The mode is the number that appears most often in a set of numbers. It is possible for a set of numbers to have no mode or multiple modes.
Dictionary DefinitionThe Oxford English Dictionary defines the mode as "the value, or range of values, of a variable which occurs most frequently in a set of data."
Finding the ModeImagine we wanted to find the mode of the numbers given below:
To find the mode, find the number that appears most often.
- 1 appears 2 times.
- 2 appears 4 times.
- 3 appears 1 time.
Understanding the ModeImagine several candidates are standing for election. The candidate with the most votes would win the election. The winning candidate would be the mode. Their name would appear most in the ballot box.
Different Numbers of ModesFor a set of numbers, there is only one mean and one median (the other types of average). However, there can be different numbers of modes: none, one or more than one.
If there are no repeated numbers in a set there is no mode. The set of numbers below has no mode:
If there is one number that apears more often that the others, there is one mode (this is called unimodal). The set of numbers below has one mode:
If there is more than one number that appear more often than the others, there is more than one mode (this is called multimodal).
The set of numbers below has two modes (1 and 2). This is called bimodal. 1 and 2 appear more often than the other numbers but equally often as each other:
The Mode Can Be Used for Non-Numeric ItemsThe other averages (the mean and the median) only apply to numbers. The mode can be used for items that are not numbers (non-numerica or categoric data). In the example used on this page, the politician that wins an election is the one with the most votes. Their name (with a voter's cross next to) appears most in the ballot box.
The Mode is a Bad Measure of Central TendencyAn average is a measure of central tendency. Although a set of numbers will have different values, their average should give you an idea of where the middle of the numbers is (where the numbers tend to center around). The mean and median do this, but the mode can do a very bad job of being in the middle. For example, consider the numbers below:
1, 1, 20, 25, 30, 35, 401 is the mode, although it does a very bad job of describing a middle or a typical number. The mean (21.7) and the median (25) are nearer the middle of the numbers.
The Mode Can Be MisleadingLook at these test results:
8%, 8%, 9%, 50%, 70%, 75%, 80%, 85%, 90%, 95%The mode is 8%. If you got 9% in the test, you could claim you got an above-average score because 9% is greater than the mode of 8%. 9% is a very low score and much worse than most students got. It is much lower than the mean score (57%) and the median score (72.5%).