[15 5] The time it takes an instructor to grade an exam
Chapter 0, Problem SE4.19(choose chapter or problem)
[15 5] The time it takes an instructor to grade an exam paper is a random variable with expected value 7.5 minutes and standard deviation 1.5 minutes. Assume that the grading times for different papers are independent. a. Using the Central Limit Theorem, find the probability that the instructor will grade 70 papers in less than 9 hours. b. Suppose the instructor grades 40 papers on one day and the remaining 30 papers on another. What is the probability that the mean times of grading a paper on both days do not exceed 7.8 minutes?
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