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1% of the parts produced by a factory are defective. Suppose the test for defective parts has a 99.5% accuracy and a 0.6% false positive rate. SUppose you pick a part and receive a positive test result. WHat is the probability that the part is indeed defective

Sagot :

Using conditional probability, it is found that there is a 0.6262 = 62.62% probability that the part is indeed defective.

Conditional Probability

[tex]P(B|A) = \frac{P(A \cap B)}{P(A)}[/tex]

In which

  • P(B|A) is the probability of event B happening, given that A happened.
  • [tex]P(A \cap B)[/tex] is the probability of both A and B happening.
  • P(A) is the probability of A happening.

In this problem:

Event A: Positive test result.

Event B: Defective.

For the probability of a positive test result, we consider two scenarios.

  • 99.5% of 1%(defective).
  • 0.6% of 100 - 1 = 99%(false positive).

Hence:

[tex]P(A) = 0.995(0.01) + 0.006(0.99) = 0.01589[/tex]

The probability of a positive test result and being defective is:

[tex]P(A \cap B) = 0.995(0.01)[/tex]

The conditional probability is:

[tex]P(B|A) = \frac{P(A \cap B)}{P(A)} = \frac{0.995(0.01)}{0.01589} = 0.6262[/tex]

0.6262 = 62.62% probability that the part is indeed defective.

A similar problem is given at https://brainly.com/question/14398287