Suppose scores of students on a test are approximately normally distributed with a mean score of 65 points and a standard deviation of 8 points. It is decided to give A's to 10 percent of the students. Obtain the threshold score that will result in an A.
Given that,
mean =
= 65
standard deviation =
= 8
Using standard normal table,
P(Z < z) = 10%
= P(Z < z) = 0.10
= P(Z <-1.28 ) = 0.10
z = -1.28
Using z-score formula
x= z *
+
x= - 1 .28 *8+65
x= 54.76
x=55
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