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Multiplicative Rule and Independent Events

48. For two events, A and B, P(A) = 0.4, P(B) = 0.2, and P(A/B)=0.6
a. find P(A and B)
b. find P(B/A)

50. An experiment results in one of three mutually exclusive events, A,B, or C. It is known that P(A) =.30,
P(B) = .55 and P (C) = .15. Find each of the following probabilities:
a. P(A U B)
b. P(A and C)
c. P(A/B)
d. P(B U C)
e. are B and C independent events? Explain

52. Two fair coins are tossed, and the following events are defined:
A: {observe at least one head}
B: {observe exactly one head}

a. Draw a Venn diagram for the experiment, showing events A and B. Assign probabilities to the sample
points.
b. Find P(A), P(B), and P(A upside down U B)
c. Use the formula for conditional probability to find P(A/B) and P(B/A). Verify your answer by inspecting the
Venn diagram and using the concept of reduced sample spaces.

54. Two fair dice are tossed and the following events are defined:
A: {sum of the numbers showing is odd}
B: {sum of the numbers showing is 9, 11, 12}
Are events A and B independent? Why

Solution Preview

48. For two events, A and B, P(A) = 0.4, P(B) = 0.2, and P(A/B)=0.6
a. find P(A and B)
Solution: P (A and B) =P(B)*P(A|B)=0.2*0.6=0.12
b. find P(B/A)
Solution: P(B|A)= P (A and B)/P(A)=0.12/0.4=0.3

50. An experiment results in one of three mutually exclusive events, A,B, or C. It is known that P(A) =.30,
P(B) = .55 and P (C) = .15. Find each of the following probabilities:
a. P(AUB)
=P(A)+P(B) =0.30+0.55=0.85
b. P(A and C)
=0
c. P(A/B)
=0
d. P(B U C)
=P(B)+P(C)=0.55+0.15=0.70
e. are B and C independent events? Explain
As B and C are mutually exclusive events, P(B and C)=0. So, P(B and C) P(B)*P(C)=0.55*0.15=0.0825.
Hence, B and C are NOT independent

52. Two fair coins are tossed, and the following events are defined:
A: {observe at least one head}
B: {observe exactly one ...

Solution Summary

The multiplicative rule and independent events are examined.

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