CONCEPT: Standard deviation depends on the following inputs

1) The number of terms in the set. (Which is given in this question as 4)

2) The gaps between the terms when arranged in increasing order

Question: Find the standard deviation of number of books read by the 4 students?

Statement 1: The range of the number of books read by the 4 students during the past month was 0

Range = Highest - Lowest = 0 (Given) i.e Highest = Lowest, i.e. Highest number of books read by any student = Lowest number of books read by any student

Since the gaps between the terms is ZERO, therefore Standard Deviation of the set = 0

SUFFICIENT

Statement 2:One of the 4 students read 5 books during the past month.The statement doesn't give any information about the gaps between the terms. The value of one term in set can NOT lead us to any conclusion about the standard deviation of the set hence

NOT SUFFICIENT

Answer: Option A

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