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4. Students in a large Mathematics class were asked to rate the course on a scale from 1 (poor) to 5 (excellent). The accompanying table shows proportions of students rating the course in each category. Rating 1 2 3 4 5 Proportion 0.05 0.17 0.25 0.33 0.2 Find the mean and standard deviation of the rating. x p(x) xp(x 5 . A company receives a very large shipment of parts. A random sample of twenty of these parts is checked and, if fewer than three are defective, the shipment is accepted. What is the probability of accepting a shipment containing: a) 8% defective (b) 15% defective? (Correct the answers to 4 decimal places)