Problem-Solving and Data AnalysisHardEffect of an outlier on the mean
Problem-Solving and Data Analysis practice question
The data set 8, 10, 10, 12 has an additional value of 30 added to it. By how much does the mean increase?
Answer: 4
Original mean = 40 ÷ 4 = 10. New mean = 70 ÷ 5 = 14. The increase is 4.
Common wrong answers
- If you answered 1
- 1 is the increase in the median (10 to 11).
- If you answered 14
- 14 is the new mean, not the increase.
- If you answered 20
- 20 is 30 − 10, the gap between the new value and the old mean, before it is spread over five values.
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