BTGmoderatorLU wrote: ↑Thu Jun 24, 2021 6:36 am
Source:Manhattan Prep
If Q is a set of consecutive integers, what is the standard deviation of Q?
1) Set Q contains 21 terms
2) The median of set Q is 20
The OA is
A
Target question: What is the standard deviation of Q?
Given: Q is a set of CONSECUTIVE integers
Statement 1: Set Q contains 21 terms.
NOTE: Standard Deviation measures dispersion (spread-apart-ness). As such, the actual values mean nothing compared to RELATIVE values.
For example, the set {1,2,3,4} has the SAME STANDARD DEVIATION as the set {6,7,8,9}
So, knowing that set Q consists of 21 CONSECUTIVE integers is SUFFICIENT.
The Standard Deviation of Q will be the same as the Standard Deviation of {1,2,3,4...20,21}
Statement 2: The median of set Q is 20.
There are several different sets that satisfy this condition.
For example, set Q could equal {19, 20, 21} or set Q could equal {18, 19, 20, 21, 22}
These two sets have DIFFERENT standard deviations.
So, statement 2 is NOT SUFFICIENT
Answer: A
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