When one strange value pulls them apart
Six scores: 20, 22, 24, 26, 28 and 30. The mean and the median are both 25. Then the last score changes to 90.
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Step 1 of 2
- Before: sixth reading 30. Mean 25, median 25.
- After: sixth reading 90. Mean 35, median still 25.
A reading far from the rest is an outlier. The 90 is one.
An outlier moves the mean toward it. The median moves much less. In this set, the median does not move at all.
The total rises by 60, from 150 to 210. The mean rises from 150 ÷ 6 = 25 to 210 ÷ 6 = 35.
The median is halfway between the middle two, 24 and 26. They do not change. So the median stays 25.