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by vinod192 » Sat Sep 10, 2011 11:46 pm
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

OA A

solution ASAP
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by bijoyajj » Sun Sep 11, 2011 12:51 am
m-2d= 58
m+ 3d =98

there for d= 8 hence mean = 74..
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by pm » Sun Sep 11, 2011 12:55 am
S.D = Distance from the mean.
Now 98 is +3 S.D and 58 is -2 S.D

Distance between 98-58 = 40 i.e 3+2 S.D so
40/5 = 8 .
Now Check :
Add 8*2 = 16 +58 = 74
8*3 = 98- 24 = 74.
A
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