SOLUTION: The grades of secondary school students on CXC's mathematics examination is normally distributed with a mean of 65% and a standard deviation of 13%. Given this information, 99% of

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Question 1101737: The grades of secondary school students on CXC's mathematics examination is normally distributed with a mean of 65% and a standard deviation of 13%. Given this information, 99% of students taking the exam score between ___ and ___.
The answer options are :

(a)25% and 75%
(b)52% and 78%
(c)35% and 95%
(d)13% and 65%

Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website!
The grades of secondary school students on CXC's mathematics examination is normally distributed with a mean of 65% and a standard deviation of 13%. Given this information, 99% of students taking the exam score between ___ and ___.
The answer options are :
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Note: 99% leaves tails of 0.005 or
(1/2)%.
Find the z-value with a left tail of 0.005
z = invNorm(0.005) = -2.5758 for the left tail; +2.5758 for the right tail
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Find the corresponding percent scores::
x = -2.5758*(0.13) + 0.65 = 0.32 = 32%
x = 2.5758*0.13 + 0.65 = 0.98 = 98%
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Cheers,
Stan H.
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(a)25% and 75%
(b)52% and 78%
(c)35% and 95%
(d)13% and 65%