Set P has n integers. What is the standard deviation of Set P?

[BTGModeratorVI]

Set P has n integers. What is the standard deviation of Set P?

(1) The range of Set P is equal to zero

(2) The mean of Set P is equal to the median of Set P

Answer: A
Source: E-gmat

[Brent@GMATPrepNow]

Set P has n integers. What is the standard deviation of Set P?

(1) The range of Set P is equal to zero

(2) The mean of Set P is equal to the median of Set P

Answer: A
Source: E-gmat

Given: Set P has n integers.

Target question: What is the standard deviation of Set P?

Statement 1: The range of Set P is equal to zero
If the range is ZERO then every element in set P must be the SAME.
If all of the values are the same then there is NO DEVIATION, which means the standard deviation of Set P is zero
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: The mean of Set P is equal to the median of Set P
There are several scenarios that satisfy statement 2. Here are two:
Case a: Set P = {1,1,1}. Since all the values are the SAME , the standard deviation is 0
Case b: Set P = {1,2,3}. Since the values are DIFFERENT, the standard deviation is NOT 0
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Answer: A

Cheers,
Brent

RELATED VIDEO FROM MY COURSE
https://www.gmatprepnow.com/module/gmat ... /video/806