Explanation

To find the standard deviation you would follow the below steps

1) Find the average (mean) of the set.

2) Find the differences between each element of the set and that average.

3) Square all the differences and take the average of the differences. This gives you the variance.

4) Take the square root of the variance.

Knowing this and performing the calculation is a bit cumbersome. However, picking numbers according to the stems should suddenly pop in your head that the answer is D.

Quantity A Picking 1, 2 , 3 , 4 , 5
Quantity B Picking 19, 18, 17, 16, 15

It is clearly different the SD. Any combination of other numbers will lead you to equal Sd or different.

This is a classic time-consuming question that you should solve more with your logic and common sense.

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