For four days of work, a clerk had daily earnings of $150, $140, $150,

Question

For four days of work, a clerk had daily earnings of $150, $140, $150, and $150 respectively. In which of the following intervals does the standard deviation of the daily earnings lie?

A) Between $140 and $150
B) Between $110 and $140
C) Between $40 and $50
D) Between $10 and $20
E) Between $0 and $10

MarkusKarl · Answer

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(140-(150*3+140)/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.

hsbinfy · Answer

147.5 is the mean .

so all numbers will lie between SD 0-10

SD is always across the mean.No need for formula here.Just find the mean and the diff fro the farthest integer(-ve or +ve diff)

that will give u the range of SD

ScottTargetTestPrep · Answer

Three of the four values are $150, and the remaining value is $140, which is $10 less than the other three. The standard deviation must be greater than $0 (since, had they been all the same, the standard deviation would be $0) and less than $10 (since the mean will be between $150 and $140, closer to $150 and since no value is far from the mean).

Answer: E

bumpbot · Answer

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For four days of work, a clerk had daily earnings of $150, $140, $150,

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For four days of work, a clerk had daily earnings of $150, $140, $150,

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