Engineering Board Exam Reviewer · Conditional Probability and Bayes' Theorem · medium
Machine A makes 60% of a factory's items and 2% of its items are defective. Machine B makes the other 40% and 5% of its items are defective. An item is chosen at random and found defective. What is the probability that it came from machine A?
- 3/5
- 3/250
- 3/8
- 5/8
Answer
C. 3/8
Solution
By Bayes' theorem: P(A D)=0.6(0.02)/0.6(0.02)+0.4(0.05)=0.012/0.032= 38.
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