Understand mean and median
Use a small example to see what the average and middle value each say about a group.
Follow the method ↓
The answer in 30 seconds
The arithmetic mean adds all observations and divides by their number. The median is the middle observation after sorting, or the mean of the two middle observations when the count is even.
For the illustrative values 2, 3, 4, 5 and 100, the mean is 22.8 while the median is 4. Report both when a very large or small value changes the picture, and describe what the values represent.
Examples to adapt
A few very high values can lift the mean above what most households pay.
A median may describe the middle experience while a mean captures total time divided across all cases.
Sample sizes, definitions and missing values matter as much as the chosen statistic.
Try your own values
Calculate mean and median
Each number represents an equally weighted observation. The calculator also displays count, minimum and maximum.
Calculated in your browser without sending or saving values. Results are rounded to four decimals. No weighting is applied; review the underlying data separately.
Follow the method
- 1Define the observations
Check unit, period, sample and treatment of missing values.
- 2Compute the mean
Add the observed numbers and divide by their count.
- 3Compute the median
Sort the values and take the central value or the average of the two central values.
- 4Explain the difference
Look for skewed distributions and unusual values; show the count and range where useful.
A closer look
See how one high value changes the summary
These fictional series contain five equally weighted observations. Only the final value changes. Units are arbitrary; neither series describes a real population.
| Sorted series | Mean | Median |
|---|---|---|
| A: 10; 12; 13; 15; 100 | 150 ÷ 5 = 30 | 13: the third value |
| B: 10; 12; 13; 15; 20 | 70 ÷ 5 = 14 | 13: the third value |
| Difference between A and B | The mean falls by 16 | The median is unchanged |
Insee distinguishes the median’s central position from the mean’s sensitivity to high values. Read both indicators alongside the observations and sample size.
Should the value 100 be removed?
That finding alone is insufficient. First check for input errors, unit differences and scope. A rare value can be correct. If you show a calculation excluding it, explain why and also show the result for the complete series.
Supporting documentation : Insee — Médiane · Consulted on 2026-10-15. Examples and calculations are illustrative.
A checklist to keep
Use these checks to record what you found. The grid supports a decision; it does not make one for you.
| Check | What to examine | Action |
|---|---|---|
| Data | Are observations comparable? | Define |
| Count | How many usable values? | Record |
| Mean | Sum divided by count? | Calculate |
| Median | Middle sorted value? | Calculate |
| Spread | Are extremes important? | Describe |
Read the checklist directly in the table.
What to check
The median does not reveal the full spread of a distribution.
A single extreme value can substantially move the mean.
Different data definitions can invalidate a comparison even when the arithmetic is correct.
Common questions
Which statistic is always better?
Neither. Choose the measure that answers the question and show enough context to interpret it.
What is the median of four values?
Sort them and average the two central values.
Sources and documentation
Documentation consulted on . Examples are illustrative; interfaces and results may change.