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I thought about this questions for a while now. I understand the fact that the foreman forgets to shut up the injection is 0.48. then the questions confuses me when they to tell us the probability of the defective molding will be produced 0.04 to 0.19 in early morning. this fact really threw me off. I am now confused. I am not even sure how to approach this problem.

A foreman for an injection-molding firm admits that on 48% of his shifts, he forgets to shut off the injection machine on his line. This causes the machine to overheat, increasing the probability that a defective molding will be produced during the early morning run from 4% to 19%. If a molding is randomly selected from the early morning run of a random day, what is the probability that it is defective?

Probability =

KGTW
  • 644
  • 4
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1 Answers1

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Hint:

Suppose there was $1$ early morning moulding a day for $10000$ days. How many defective mouldings might you expect? Fill in the question marks beloe

  • on ????? days you would expect the machine to overheat, and so you would expect ???? defective mouldings from those days

  • on ????? days you would expect the machine not to overheat, and so you would expect ???? defective mouldings from those days

  • so in total you would expect ???? defective mouldings out of $10000$, so the probability of a defective moulding is ????

Henry
  • 157,058
  • on 4800 days you would expect the machine to overheat, and so you would expect 19 % defective mouldings from those days

    on 5200 days you would expect the machine not to overheat, and so you would expect 4% defective mouldings from those days

    so in total you would expect 1120 defective mouldings out of 10000, so the probability of a defective moulding is 0.112
    – KGTW Oct 06 '13 at 01:40
  • Thank you very much for the help. – KGTW Oct 06 '13 at 01:40