The variance of a set of numbers is 9. What is the standard deviation?
A81
B4.5
C3CORRECT
D√3
GCEFurther MathematicsProbability and Statistics2020
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Why the answer is C, and why the others tempt you.
Standard deviation is the square root of the variance. √9 = 3. Option A (81) is the square of the variance, option B (4.5) is half the variance, and option D confuses the relationship between the two measures.
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