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# Principal of a school recorded the number of students in each of 15 cl

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Re: Principal of a school recorded the number of students in each of 15 cl [#permalink]
The standard deviation of the number of students in the 15 classes

Given that the average number of students for all the classes = 30

But, we do not have any information about the number of students in each class.

Therefore, Statement 1 alone is not sufficient to answer this question.

Therefore, Statement 2 alone is sufficient to answer this question
Option B
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Re: Principal of a school recorded the number of students in each of 15 cl [#permalink]
Q: std. deviation between # students in 15 classes

S1: avg
S2: each class same # students

S1: insufficient --> average is not enough to determine std. Says nothing about dispersion.

S2: each class same # students --> so difference of them from median 0 , # students class A = # students each other class = avg. the same too , so data points do not deviate from mean = Standard deviation 0

Hence, B imo.
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Re: Principal of a school recorded the number of students in each of 15 cl [#permalink]
If the number of students in each class is the same; there is no deviation between the classes. In other words, zero deviation.

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Re: Principal of a school recorded the number of students in each of 15 cl [#permalink]
DavidTutorexamPAL wrote:

This question is resolved using the logic of standard deviation - SD is a measure of how spread out an average is. To find it, we need info about the variance of the values being checked, or the values themselves (the number of students in each class). Without that information, finding standard deviation is impossible.

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Re: Principal of a school recorded the number of students in each of 15 cl [#permalink]
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Re: Principal of a school recorded the number of students in each of 15 cl [#permalink]
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