Sagot :
Answer:
a) 0.4658 = 46.58% probability that the chosen ball is blue
b) 0.322 = 32.2% probability that it came from the first urn
Step-by-step explanation:
A probability is the number of desired outcomes divided by the number of total outcomes.
Conditional Probability
We use the conditional probability formula to solve this question. It is
[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.
a. What is the probability that the chosen ball is blue?
6/20 = 0.3 of 0.5(first urn)
12/19 = 0.6316 out of 0.5(second urn).
So
[tex]P(A) = 0.3*0.5 + 0.6316*0.5 = 0.4658[/tex]
0.4658 = 46.58% probability that the chosen ball is blue.
b. If the chosen ball is blue, what is the probability that it came from the first urn?
Event A: Blue Ball
Event B: From first urn
From item a., [tex]P(A) = 0.4658[/tex]
Probability of blue ball from first urn:
0.3 of 0.5. So
[tex]P(A \cap B) = 0.3*0.5 = 0.15[/tex]
Probability:
[tex]P(B|A) = \frac{P(A \cap B)}{P(A)} = \frac{0.15}{0.4658} = 0.322[/tex]
0.322 = 32.2% probability that it came from the first urn