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For a certain very large group of students, test scores are normally distributed with a mean...

For a certain very large group of students, test scores are normally distributed with a mean of 70 and a standard deviation of 8. A student will receive an A if he gets at least a 92, and must earn at least a 67 in order to pass.

a. What is the probability that a student selected at random will get an A on the test?

b. What is the probability that a random sample of 20 students will have an average grade of below 67?

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