es of 20 parts from a metal punching process are selected every hour. Typically,
ID: 2933272 • Letter: E
Question
es of 20 parts from a metal punching process are selected every hour. Typically, 1% of the parts require rework. Let Ns denote the number of parts in the sample of 20 that require rework a) A process problem is suspected if N, exceeds its mean by more than three standard deviations. If the percentage of parts that require rework remains at 1%, what is the probability that a process problem is nevertheless suspected? b) If the rework percentage is actually 4%, what is the probability that N, exceeds 1? c) If the rework percentage is actually4%.what i, the probability that Na exceeds linat b. 0.1897 c. 0.6506 least one of the next ive hours of samples? d) If the rework percentage is actually 4%, what is the probability that more than two hours d. 0.1954 of sampling will be required to find the first part which requires rework?Explanation / Answer
probabilty that no defective part found in first hour =P( no defective unit in 20 units) =(0.96)20 =0.4420
hence probability that more then 2 two hours required =P( no defective in first 2 sample)
=(0.4420)*(0.4420)=0.1954
hence option D is correct.
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