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Students are unprepared for a multiple choice quiz with 25 questions. Each question has...

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joshknr | eNoter

Posted May 21, 2013 at 12:55 AM via iOS

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Students are unprepared for a multiple choice quiz with 25 questions. Each question has 5 possible answers. Find mean and standard deviation.

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llltkl | College Teacher | Valedictorian

Posted May 21, 2013 at 1:55 AM (Answer #1)

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Students are unprepared for a multiple choice quiz with 25 questions. Each question has 5 possible answers.

Let, out of 5 possible answers only one is correct.

Therefore, P(correct)=1/5=0.20

Hence, mean=n*p=25*0.20=5  (n=no. of questions and p=proportion of correct answers)

Standard deviation=`sqrt(n*p*(1-p))` where n=no. of questions and p=proportion of correct answers

Here, n=25,p=0.20. Now putting the values we get:

`sqrt(25*0.20*(1-0.20))`

`=sqrt(25*0.20*080)`

`=sqrt(4)` =2

Therefore, mean=5, standard deviation=2.

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