Sandeepanisha wrote:
Hi karishma,
I need help in this question
1/ (statistics) 21 students took an exam. What is the number of students whose scores are at least the average (arithmetic mean) score of them?
1) The average (arithmetic mean) score of them is 78
2) The median score of them is 78
Hey Sandeepanisha,
We have 21 total students. We need those who scored >= Average
1) The average (arithmetic mean) score of them is 78
Not sufficient. We don't know how many scored at or above average and how many scored below average. There are many cases possible.
E.g. All 21 students scored exactly 78.
or 1 student scored 77, 19 students scored 78 and 1 student scored 79
and so on...
Number of students who scored >= average will be different in each case.
2) The median score of them is 78
Median score is the 11th score (middle) when all are arranged in increasing order. Again, multiple cases are possible.
E.g. All 21 students scored exactly 78. (so 11th score is also 78)
or 1 student scored 77, 19 students scored 78 and 1 student scored 79 etc (so 11th score is also 78)
and so on...
Number of students who scored >= average will be different in each case.
Using both statements, even if we know that the average is 78 and median is 78 too, still multiple cases are possible. Both examples discussed above hold and number of students who scored atleast average is different in both examples.
Answer (E)
_________________
Karishma
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