For four days of work, a clerk had daily earnings of $160, $150, $160, and $160 respectively. In which of the following intervals does the standard deviation of the daily earnings lie? Choose the correct choice.
A) Between $10 and $50
B) Between $0 and $10
C) Between $20 and $25
D) Between $50 and $100
E) Between $50 and $65
The standard deviation is between 0 and 10.   The reason is that none of the numbers in the set is further away from the mean than 10(or rather Abs(150-(160*3+150)/4)). I am not fully sure how to calculate the standard deviation(I simply remember that there were some formula for calculating the average of the squared distances from the mean for all items in the set from statistics classes - variation), but I believe this will suffice for any GMAT question related to standard deviation.   Answer : Between $0 and $10
<result>B</result>
For four days of work, a clerk had daily earnings of $160, $150, $160, and $160 respectively. In which of the following intervals does the standard deviation of the daily earnings lie?