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Problem-Solving and Data AnalysisVery hardEffect on mean and median of raising the largest value

Problem-Solving and Data Analysis practice question

A data set has five values with a mean of 20 and a median of 18. The largest value is increased by 10 and the other values are unchanged. Which of the following describes the new mean and median?

  1. A. The mean rises to 22, and the median is unchanged at 18.Correct
  2. B. The mean and the median both rise by 10.
  3. C. The mean is unchanged, and the median rises to 28.
  4. D. The mean rises to 30, and the median rises to 20.

Answer: A. The mean rises to 22, and the median is unchanged at 18.

The total rises by 10, so the mean rises by 10/5 = 2; the middle value is untouched.

Why the other answers are wrong

B. The mean and the median both rise by 10.
The median does not depend on how large the largest value is.
C. The mean is unchanged, and the median rises to 28.
The mean changes; the median does not.
D. The mean rises to 30, and the median rises to 20.
The mean rises by 2, not 10.

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