If a certain sample of data has a mean of 20.0 and a standard deviation of 3.0, which of the following values is more than 2.5 standard deviations from the mean?
a) 12.0
b) 13.5
c) 17.0
d) 23.5
e) 26.5
GMAT prep question 2
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This might be represented algebraically as |X-20| ≥ 7.5weipei wrote:Can you explain little bit more on the answer? Thanks!
When given X, the value on the left side of the equation will yield some difference between X and the mean. That difference must be greater than 2.5 times the standard deviation of 3.0 - in other words, 7.5.
At this point it's only a matter of solving for values that satisfy the equation. (A) serves up the only number that qualifies.