Mean, Median, Mode, and Range
These four measures describe the center and spread of a data set. Together they give a quick summary of the data's distribution without needing a full statistical analysis.
Formulas
| Measure | Formula | Best For |
|---|---|---|
| Mean | Sum ÷ Count | Symmetric data, general average |
| Median | Middle value (sorted) | Skewed data, outlier resistance |
| Mode | Most frequent value | Categorical data, finding peaks |
| Range | Max − Min | Quick spread estimate |
| Geometric Mean | ⁿ√(x₁ × x₂ × ... × xₙ) | Growth rates, ratios |
Examples
Example 1: Test Scores
Data: 72, 85, 90, 85, 78
- Mean: (72 + 85 + 90 + 85 + 78) ÷ 5 = 82
- Median: Sorted = 72, 78, 85, 85, 90 → middle = 85
- Mode: 85 (appears twice)
- Range: 90 − 72 = 18
Example 2: Skewed Data
Data: 30, 35, 32, 31, 250 (one outlier)
- Mean: 75.6 (pulled up by outlier)
- Median: 32 (better represents the "typical" value)
This shows why median is preferred for skewed data — the mean is misleading here.
Mean vs Median
| Mean | Median | |
|---|---|---|
| Outlier sensitivity | Highly sensitive | Resistant |
| Skewed data | Misleading | More representative |
| Symmetric data | Equal to median | Equal to mean |
| Common use | GPA, test averages | Income, house prices |
When There Is No Mode
If all values appear the same number of times (e.g., all unique), there is no mode. If multiple values tie for highest frequency, the data set is multimodal — all tied values are modes.