3. -/3 points Devor eStat92E034 My Notes Ask Your Teacher + Computer keyboard fa

Question

3. -/3 points Devor eStat92E034 My Notes Ask Your Teacher + Computer keyboard failures can be attributed to electrical defects or mechanical defects. A repair facility currently has 25 failed keyboards, 11 of which have electrical defects and 14 of which have mechanical defects. (a) How many ways are there to randomly select 5 of these keyboards for a thorough inspection (without regard to order)? ways (b) In how many ways can a sample of 5 keyboards be selected so that exactly two have an electrical defect? ways (c) If a sample of 5 keyboards is randomly selected, what is the probability that at least 4 of these will have a mechanical defect? (Round your answer to four decimal places.) Need Help?Read It Talk to a Tutor

Explanation / Answer

a) Number of ways to slect 5 of these keyboards = 25C5 = 25! / (5! * (25-5)!) = 53130

b) Number of ways to have exactly two electrical defect = 11C2 * 14C3 = 55 * 364 = 20020

c) P(at least 4 will have mechanical defect) = P(4 mechanical defect) + P(5 mechanical defect)

                                                = (14C4 * 11C1 / 25C5) + (14C5 / 25C5)

                                                = 11011/53130 + 2002/53130

                                                = 0.2449

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