Calculateur moyenne, mediane et mode

Mean Median Mode Calculator

The mean, median, and mode are the three main ways to describe the center of a data set — each answering a slightly different question. The mean tells you the arithmetic average. The median tells you the middle value after sorting. The mode tells you the most frequently occurring value. Choosing the right measure depends on your data’s distribution and what you are trying to communicate. This calculator computes all three instantly, along with the range and count, so you can compare them side by side.

How Each Measure Is Calculated

Mean = Sum of all values / Count of values Sort not required. Add everything up, divide by n. Example: (4 + 7 + 7 + 10 + 12) / 5 = 40 / 5 = 8.

Median = Middle value of a sorted list Sort the values in order. For an odd count, the median is the center value. For an even count, average the two center values. Example: sorted list {4, 7, 7, 10, 12} — median is 7 (position 3 of 5). For {4, 7, 10, 12}: median = (7 + 10) / 2 = 8.5.

Mode = Value(s) appearing most often Count how many times each value appears. The mode is the value with the highest frequency. A data set can have one mode, two or more modes (bimodal/multimodal), or no mode if all values appear exactly once.

Range = Maximum value — Minimum value. Measures total spread.

Worked Examples

Example 1 — Symmetric, well-behaved data set: {12, 14, 14, 16, 18, 20, 20, 20, 22} Mean: (12+14+14+16+18+20+20+20+22) / 9 = 156 / 9 = 17.33. Median: 9 values, center is position 5 = 18. Mode: 20 (appears 3 times). Range: 22 - 12 = 10. Mean and median are close (17.33 vs. 18), confirming near-symmetry.

Example 2 — Outlier-skewed income data: {42000, 45000, 47000, 49000, 51000, 380000} Mean: 614,000 / 6 = $102,333. Median: average of positions 3 and 4 = (47,000 + 49,000) / 2 = $48,000. Mode: none (all unique). Range: $338,000. The mean of $102,333 is more than double the median of $48,000 — the $380,000 outlier drags the mean far from where most values cluster. The median is the better “typical” value here.

Example 3 — Retail shoe sizes: {7, 7, 8, 8, 8, 9, 9, 10, 11} Mean: 77 / 9 = 8.56. Median: position 5 = 8. Mode: 8 (appears 3 times). Range: 4. For a store manager deciding which size to stock most, the mode (8) is the most actionable number — it tells you the single most common size, which neither the mean nor median directly indicates.

Central Tendency Reference Table

When to Use This Calculator

• Summarizing test scores — the mean works well when score distributions are fairly normal and no student scored absurdly high or low
• Reporting income or home prices — use the median to represent “typical” when a few high values would inflate the mean above what most people actually earn or pay
• Quality control data — compare mean and median to detect whether a production process is generating outliers that skew your average output measurement
• Survey responses on a Likert scale — the mode identifies the most commonly selected response, which is often more interpretable than a decimal mean like 3.7 out of 5
• Identifying data errors — a large gap between mean and median often signals a data entry mistake or a genuine outlier worth investigating

Common Mistakes

1. Calling the mean “the average” without specifying — in everyday speech, “average” usually means mean, but in statistics it can refer to any measure of central tendency. When reporting data, specify which measure you used to avoid misinterpretation.
2. Forgetting to sort before finding the median — the median depends entirely on the sorted order; the middle value of an unsorted list is meaningless. Always sort from smallest to largest first.
3. Assuming no mode means the data has no center — a data set with all unique values has no mode, but still has a meaningful mean and median. No mode just means no single value repeats, not that the data is centerless.
4. Using the mean for skewed data — for income, home prices, response times, or any data where a few extreme values are common, the mean overstates the typical case. Check whether mean and median are close before choosing mean as your summary statistic.

Context and Applications

These three measures appear throughout statistics, data analysis, journalism, and everyday decision-making. When the US Census Bureau reports household income, it publishes the median — not the mean — because the mean would be pulled upward by high-income households and misrepresent what a typical family earns. Sports analysts use batting averages (a mean) because the distribution of at-bat outcomes is relatively stable. Epidemiologists tracking disease incubation periods often report the median because the distribution is right-skewed. Understanding which measure to apply — and why — is one of the first and most practical skills in data literacy.

Tips

• If the mean and median differ by more than about 10% of the range, the data is likely skewed — report the median and note the skew rather than defaulting to the mean
• For very small data sets (n less than 5), all three measures become less stable; a single value change can shift the mode entirely or flip the median
• Always state the sample size alongside any central tendency measure — a mean of 47 from 300 observations is far more reliable than a mean of 47 from 4 observations
• The mode is the only measure that works for non-numerical (categorical) data; you cannot average colors or names, but you can find the most frequent one
• Range is quick to compute but a single outlier can make it misleading — if you need to describe spread more reliably, also note the interquartile range (Q3 minus Q1)
• When presenting data to a general audience, pair the median with the range or show a simple histogram — a single number almost never tells the full story