Bunuel wrote:

Is the standard deviation of Set A greater than or equal to the standard deviation of Set B?

(1) Set B can be formed by dividing each value in Set A by 4.

(2) Set A consists of 7 unique numbers.

Question : Is Standard Deviation of A > Standard deviation of B?Statement 1: Set B can be formed by dividing each value in Set A by 4.Since each value of A is divided by 4 to obtain each value of Set B therefore the gaps among the values will also be divided by 4 hence standard deviation will decrease hence

Standard Deviation of A

> Standard deviation of B

SUFFICIENT

Statement 2: Set A consists of 7 unique numbersNo Information of Set B hence

NOT SUFFICIENT

Answer: option A

CONCEPT TABLE ON STANDARD DEVIATIONSTANDARD DEVIATION

Standard Deviation : Average Deviation of Terms of a set from the Mean value of the Set1) If we had assumed that all barrels had the same amount of mixture then standard deviation would have been zero. Non Zero standard deviation means that all barrels don't have the same amount of Mixture and the the size of Barrels doesn't matter, all that matters is the amount of Mixture in the barrels

2) The standard deviation of a set doesn't change if a constant is added to/subtracted from each terms of the set

e.g.{1, 2, 3, 4, 5} will have same standard Deviation as {1

+10, 2

+10, 3

+10, 4

+10, 5

+10}

Reason: The deviation remains same as before if the constant is added to/Subtracted from each term3) Standard Deviation of the Set changes when a constant term which is not equal to 1 is multiplied with/divides every terms of the set

e.g. {0.7, 1.4, 2.1, 2.8, 3.5} will have Standard Deviation = 0.7* Standard deviation of set {1, 2, 3, 4, 5}

Reason: The deviation gets multiplied by or divided by the same constant that every terms is multiplied or divided with
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