Answer :
Answer:
There is a 90.46% probability that it was repaired by a competent shop, given that it was repaired correctly.
Step-by-step explanation:
We have these following probabilities:
An 87% probability that an air conditioner repair shop is competent.
A 13% probability that an air conditioner repair shop is incompetent.
An 85% probability that an compotent shop can repair the air.
A 60% probability than an incompetent shop can repair the air.
This can be formulated as the following problem:
What is the probability of B happening, knowing that A has happened?
It can be calculated by the following formula
[tex]P = \frac{P(B).P(A/B)}{P(A)}[/tex]
Where P(B) is the probability of B happening, P(A/B) is the probability of A happening knowing that B happened and P(A) is the probability of A happening.
In this problem we have that:
Probability that it was repaired by a competent shop, given that it was repaired correctly.
P(B) is the probability that it was repaired by a competent shop. 87% of the shops are competent, so [tex]P(B) = 0.87[/tex]
P(A/B) is the probability that it was repaired correctly, given that it was repaired by a competent shop. There is an 85% probability that an compotent shop can repair the air. So [tex]P(A/B) = 0.85[/tex]
P(A) is the probability that an air was repaired correctly.
This is 85% of 87% and 60% of 13%. So
[tex]P(A) = 0.85*0.87 + 0.60*0.13 = 0.8175[/tex]
Finally
[tex]P = \frac{P(B).P(A/B)}{P(A)} = \frac{0.87*0.85}{0.8175} = 0.9046[/tex]
There is a 90.46% probability that it was repaired by a competent shop, given that it was repaired correctly.