Mean, Median & Mode

The three measures of central tendency — what they are and when to use each

Explanation

These three values all describe the "center" of a dataset, but in different ways.

Mean — the average. Add all values, divide by count. `` [2, 4, 4, 4, 5, 5, 7, 9] → mean = 40 / 8 = 5.0

Median — the middle value when sorted. If even count, average the two middle values. `` [2, 4, 4, 4, 5, 5, 7, 9] → median = (4+5)/2 = 4.5

Mode — the most frequent value. `` [2, 4, 4, 4, 5, 5, 7, 9] → mode = 4

When each matters:

Mean: works well for symmetric data with no outliers
Median: better when outliers exist (e.g. income data — one billionaire skews the mean)
Mode: only useful measure for categorical data (e.g. most common shoe size)

Examples

Computing all three in Python

Python's statistics module handles all three

import statistics

data = [2, 4, 4, 4, 5, 5, 7, 9]
print(statistics.mean(data))    # 5.0
print(statistics.median(data))  # 4.5
print(statistics.mode(data))    # 4

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Variance & Standard Deviation

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