Mode - The Most Common Value
The mode is the value that appears most often in a dataset. It is the only average that can be used for non-numerical data, such as the most popular colour or the most common category in a survey.
The statistical term “mode” was introduced by the same statistician who coined “histogram” and “standard deviation,” Karl Pearson, in the 1890s, borrowing the French phrase à la mode (“in fashion”) to describe the most fashionable, most frequently occurring value in a dataset. That fashion connection is fittingly literal in the clothing industry: shoe and clothing manufacturers rely heavily on the mode when deciding stock levels, since knowing the single most commonly sold size lets a retailer order far more of that size than the rarer ones, avoiding both wasted stock and missed sales.
Key Facts About the Mode
- A dataset can have one mode (unimodal), two modes (bimodal), or more than two modes (multimodal).
- If every value appears the same number of times, there is no mode.
- The mode is the only average suitable for qualitative (categorical) data.
- The mode is not affected by outliers.
Worked Examples
Tally: 3 appears 3 times; 7 appears 2 times; 5 and 9 appear once. Mode = 3.
4 appears twice; 6 appears twice; 1 and 9 appear once. Two modes: 4 and 6 (bimodal).
Apple: 3 times, Banana: 2 times, Mango: 2 times. Mode = Apple. (Non-numerical data – only mode applies.)
Highest frequency = 12, in class 160–170 cm. Modal class = 160–170 cm.
Comparing Mode, Median, and Mean
| Average | Uses every value? | Affected by outliers? | Works for categories? |
|---|---|---|---|
| Mean | Yes | Yes | No |
| Median | No | No | No |
| Mode | No | No | Yes |
Key Takeaways
- Mode = the most frequent value or category.
- A dataset can have no mode, one mode, or several modes.
- Use the mode when you need the most common item, especially for qualitative data.
- For grouped data, identify the modal class (the class with the highest frequency).