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Central Tendency — Mean, Median, and Mode

5 min readGrade 8 · Data & Probability

Mean, median, and mode each answer 'what is typical?' differently. The mean balances the data, the median marks the middle, and the mode is the most common value. One outlier pulls the mean but leaves the median steady.

What students explore

Students compute mean, median, and mode, decide which best describes a data set, and investigate how outliers shift each measure.

Key ideas

Mean = sum ÷ count. Median = the middle value of the ordered data (the average of the two middle values if the count is even). Mode = the most frequent value. The median resists outliers; the mean does not.

Worked example

For 4, 7, 7, 9, 13: mean = 40 ÷ 5 = 8; median = 7 (middle value); mode = 7. Replace 13 with 53: the mean jumps to 16, but the median stays 7 — the outlier moves the mean only.

KEY VOCABULARY

Mean — The sum of the values divided by the number of values.

Median — The middle value when the data is ordered.

Mode — The value that occurs most often in a data set.

Outlier — A value much larger or smaller than the rest of the data.