Here are the solutions to the questions.
Question 1:
Given: P(A)=21, P(A∩B)=92, P(A∪B)=97.
a) Calculate P(B)
Step 1: Use the formula for the probability of the union of two events.
P(A∪B)=P(A)+P(B)−P(A∩B)
Step 2: Substitute the given values into the formula.
97=21+P(B)−92
Step 3: Solve for P(B).
P(B)=97−21+92
P(B)=99−21
P(B)=1−21
P(B)=21
a) 21
b) Calculate P(A∣B)
Step 1: Use the formula for conditional probability.
P(A∣B)=P(B)P(A∩B)
Step 2: Substitute the known values for P(A∩B) and P(B).
P(A∣B)=2192
Step 3: Simplify the expression.
P(A∣B)=92×12
P(A∣B)=94
b) 94
c) Calculate P(A′∩B)
Step 1: Use the relationship between P(B), P(A∩B), and P(A′∩B).
P(A′∩B)=P(B)−P(A∩B)
Step 2: Substitute the known values for P(B) and P(A∩B).
P(A′∩B)=21−92
Step 3: Find a common denominator and subtract.
P(A′∩B)=189−184
P(A′∩B)=185
c) 185
Question 2:
Let LA be the event that a voter preferred List A, and LB be the event that a voter preferred List B.
Let M be the event that a voter preferred a male candidate, and F be the event that a voter preferred a female candidate.
Given probabilities:
P(LA)=0.60
P(LB)=0.40
P(M∣LA)=0.70
P(F∣LA)=0.30
P(M∣LB)=0.60
P(F∣LB)=0.40
1) Draw a tree diagram to illustrate this information.
Start
|
|-- P(L_A) = 0.60 --|-- P(M|L_A) = 0.70 --> Male from List A (M_A)
| |-- P(F|L_A) = 0.30 --> Female from List A (F_A)
|
|-- P(L_B) = 0.40 --|-- P(M|L_B) = 0.60 --> Male from List B (M_B)
|-- P(F|L_B) = 0.40 --> Female from List B (F_B)
2) Calculate the probability that:
a) A female candidate wins.
Step 1: Calculate the probability of a female candidate from List A.
P(F∩LA)=P(F∣LA)×P(LA)=0.30×0.60=0.18
Step 2: Calculate the probability of a female candidate from List B.
P(F∩LB)=P(F∣LB)×P(LB)=0.40×0.40=0.16
Step 3: Sum these probabilities to find the total probability