SOLUTION: A recent examination given by your statistics instructor has been scored. The mean was 78 and a standard deviation of 7. Assume that a standard scale of 90-100 A, 80-<90 B, 70-<80

Question 320570: A recent examination given by your statistics instructor has been scored. The mean was 78 and a standard deviation of 7. Assume that a standard scale of 90-100 A, 80-<90 B, 70-<80 C, 60-<70 D, 0-<60 F.

Not sure where to begin.... Thank you in advance for your help!
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
A random sample of n = 4 scores is obtained from a normal
population with meu= 20 and sigma= 4.
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What is the probability of obtaining a mean greater than
M = 22 for this sample?
-----
sample mean = 22
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t(22) = (22-20)/[4/sqrt(4)] = 2/(4/2) = 1
-----------------------------
P(x-bar> 22) = P(t > 1 when df=3) = tcdf(1,1000,3) = 0.1955
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Cheers,
Stan H.

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