SAT Math: Effect of an Outlier on Mean, Median, and Range
25+ practice questions in Praczo
The concept, explained
- 1
The mean is heavily affected by outliers — one extreme value significantly pulls it toward that extreme.
- 2
The median is resistant to outliers. Adding an extreme value usually changes the median by at most one position.
- 3
The range always increases (or stays the same) when an outlier more extreme than the current max or min is added.
- 4
When a dataset contains an outlier, the median is typically a better measure of center because it isn't distorted.
- 5
The SAT often asks: "If the largest value is removed, which measures change?" Mean decreases; range decreases (new max is smaller); median may or may not change.
- ✗ Assuming the median is completely unaffected by additions. Adding a new middle value to an even-sized dataset can shift the median.
- ✗ Confusing "the range changes" with "the range increases." Range increases only when the outlier is more extreme than the current max or min.
SAT-style practice
A data set contains: 4, 7, 8, 9, 11. The value 50 is added. Which best describes the effect on the mean and median?
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