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25 Oct 2018, 02:22
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B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
25%
(medium)
Question Stats:
70% (00:43) correct
30%
(01:05)
wrong
based on 134
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Principal of a school recorded the number of students in each of 15 classes. What was the standard deviation of the numbers of students in the 15 classes?
(1) The average (arithmetic mean) number of students for all the classes was 30.
(2) Each classes had the same number of students.
(1) The average (arithmetic mean) number of students for all the classes was 30.
(2) Each classes had the same number of students.
25 Oct 2018, 04:18
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The answer is E.
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.
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.
25 Oct 2018, 06:34
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Solution
Given:
- • The total number of classes = 15
To find:
- • The standard deviation of the number of students in the 15 classes
Analysing Statement 1
- • 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.
Analysing Statement 2
- • Given that each class had the same number of students
- o Thus, deviation = 0
Therefore, Statement 2 alone is sufficient to answer this question
Hence, the correct answer is Option B
Answer: B
