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please help me out

by B166418 » Wed Jun 29, 2011 10:54 am
For a certain examination,a score of 58 was 2 standard deviations below the mean,and a score of 98 was 3 standard deviations above the mean .What was the mean score for the examination ?

A 74
B 76
C 78
D 80
E 82
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by Frankenstein » Wed Jun 29, 2011 11:05 am
Hi,
If 'm' is the mean and 'd' is the standard deviation, from the given data
m - 2d = 58
m + 3d = 98
Solving, we get d= 8 and m = 74

Hence, A
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by B166418 » Wed Jun 29, 2011 11:31 am
Wow!!! and I was applying standard deviation and mean formulas in this problem
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by MBA.Aspirant » Wed Jun 29, 2011 1:43 pm
B166418 wrote:For a certain examination,a score of 58 was 2 standard deviations below the mean,and a score of 98 was 3 standard deviations above the mean .What was the mean score for the examination ?

A 74
B 76
C 78
D 80
E 82
m - 2d= 58

m + 3d = 98

5d = 40

d = 8

m = 98 - 3 (8) = 74
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