16Hit1600
Problem-Solving and Data AnalysisMediumComparing standard deviations by eye

Problem-Solving and Data Analysis practice question

Which of the following data sets has the greatest standard deviation?

  1. A. 1, 1, 9, 9Correct
  2. B. 4, 5, 5, 6
  3. C. 5, 5, 5, 5
  4. D. 3, 5, 5, 7

Answer: A. 1, 1, 9, 9

All four sets have mean 5. Standard deviation measures how far values sit from the mean: in set A every value is 4 away, which is more than any other set's spread.

Why the other answers are wrong

B. 4, 5, 5, 6
Values 1 or 0 away from the mean — a small spread.
C. 5, 5, 5, 5
All values equal the mean, so the standard deviation is 0.
D. 3, 5, 5, 7
Values 2 or 0 away from the mean — less spread than set A's 4.

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