Correct Answer: D
Explanation:
Arithmetic Statistics
In determining the standard deviation, the difference between each measurement and the mean is squared, and then the squared differences
are added and divided by the number of measurements. The quotient is the variance and the positive square root of the variance is the
standard deviation.
- (1) If the variance is 4, then the standard deviation = √4 = 2, which is less than 3; SUFFICIENT.
- (2) For each measurement, the difference between the mean and that measurement is 2.
Therefore, the square of each difference is 4, and the sum of all the squares is 4 X 20 = 80.
The standard deviation is √ 80/20 = √4 = 2, which is
less than 3; SUFFICIENT.
The correct answer is D; each statement alone is sufficient.
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