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1. A population of 600 semiconductor wafers contain wafers from the lots. The wa

ID: 3064118 • Letter: 1

Question

1. A population of 600 semiconductor wafers contain wafers from the lots. The wafers are categorized by lot and by whether they conform to a thickness specification. The following table presents the number of wafers in each category.A wafer is chosen at random from the population Lot Conforming nonconforming 165 260 12 35 40 a. If the wafer is from list A, what is the probability that b. If the wafer is conforming, what is the probability that c. If the wafer is conforming, what is the probability that d. If the wafer is not from lot C, what is the probability it is conforming? is from lot A? it is not from lot C? tha is conforming?

Explanation / Answer

a) P(conforming | lot A) = P(conforming and lot A) / P(lot A)

                                      = (88/600) / ((88+12)/600)

                                      = 88 / 100

                                      = 0.88

b) P(lot A | conforming) = P(conforming and lot A) / P(conforming)

                                      = (88/600) / ((88+165+260)/600)

                                      = 88 / 513

                                      = 0.1715

c) P(not from lot C | conforming) = 1 - P(lot C | conforming)

                                                    = 1 - P(conforming and lot C) / P(conforming)

                                                    = 1 - [(260/600) / ((88+165+260)/600)]

                                                    = 1 - (260 / 513)

                                                    = 0.4932

d) P(conforming | not from lot C) = P(conforming and not from lot C) / P(not from lot C)

                                                     = ((88+165)/600) / ((88+12+165+35)/600)

                                                     = 253 / 300

                                                     = 0.8433