Question

Three methods, A, B and C, are available for teaching a certain industrial skill. The failure rate is 15% for A, 5% for B and 10% for C. The method A is used 30%, B is used 40% and C is used 30% of the time. A worker is taught the skill by one of the methods but fails to learn it correctly. a. (10 points) What is the probability that he was taught by method A? b. (5 points) What is the probability of B given A?

Answer 1

a) so the correct answer is that the probability that method A has been taught is 0.4737

b) the probability that B receives A is 0.5

Explanation:

With the previous data we know that 3 methods teach an industrial skill and when putting into practice a worker does not learn, we have the failure rates like this:

method A fails 15%

method B fails: 5%

method C fails: 10%

usage percentages:

A: 30%

B: 40%

C: 30%

a) the probability that method A has been taught is as follows:

P (failure rate) = P (A) * P (failure rate A) + P (B) * P (failure rate B) + P (C) * P (failure rate C)

we replace the data obtaining:

P = 0.3 * 0.15 + 0.4 * 0.05 + 0.3 * 0.1 = 0.095

P ( failure rate A) = P (A) * P (failure rate A) / P (failure rate)

we replace the data obtaining:

0.3 * 0.15 / 0.095 = 0.4737

so the correct answer is that the probability that method A has been taught is 0.4737

b) the probability that B receives A is as follows:

P (B | A) = P (B) = 0.50