Respuesta :
Answer:
a. The probability that the finished product selected is defective is 2.45%.
b. The probability that product chosen randomly was defective and made by machine B3 is 20.41%.
Step-by-step explanation:
Let A represents the defective product.
We also have the following from the question:
P(B1) = Probability or percentage of the made by machine B1 = 30%, or 0.30
P(B2) = Probability or percentage of the made by machine B2 = 45%, or 0,45
P(B3) = Probability or percentage of the made by machine B3 = 25%, or 0.25
P(A/B1) = Probability or percentage of product B1 that is defective = 2%, or 0.02
P(A/B2) = Probability or percentage of product B2 that is defective = 3%, or 0.03
P(A/B3) = Probability or percentage of product B3 that is defective = 2%, or 0.02
We can therefore proceed as follows:
A. Suppose that a finished product is randomly selected. What is the probability that it is defective?
To determine this, the rules of elimination is applied and we have:
P(A) = (P(B1) * P(A/B1)) + (P(B2) * P(A/B2)) + (P(B3) * P(A/B3)) ………… (1)
Where;
P(A) = Probability that the selected product is defective = ?
Substitutes the values defined above into equation (1), we have:
P(A) = (0.30 * 0.02) + (0.45 * 0.03) + (0.25 * 0.02)
P(A) = 0.006 + 0.0135 + 0.005
P(A) = 0.0245, or 2.45%
Therefore, the probability that the finished product selected is defective is 2.45%.
B. If a product were chosen randomly and found to be defective, what is the probability that it was made by machine B3.
To calculate this, the Bayes’ rule is employed as follows:
P(B3/A) = (P(B3) * P(A/B3)) / [(P(B1) * P(A/B1)) + (P(B2) * P(A/B2)) + (P(B3) * P(A/B3))] = (P(B3) * P(A/B3)) / P(A) ………….... (2)
Where;
P(B3/A) = The probability that product chosen randomly was defective and made by machine B3 = ?
Also, from the values already defined and obtained in part A, we have:
P(B3) = 0.25
P(A/B3) = 0.002
P(A) = 0.0245
Substituting the values into equation (2), we have:
P(B3/A) = (0.25 * 0.02) / 0.0245
P(B3/A) = 0.005 / 0.0245
P(B3/A) = 0.2041, or 20.41%
Therefore, the probability that product chosen randomly was defective and made by machine B3 is 20.41%.
