Question

In a recent month, 88% of automobile drivers filled their vehicles with regular gasoline, 2% purchased midgrade gas, and 10% bought premium gas. Given that a driver bought regular gas, 28% paid with a credit card; given that they bought midgrade and premium gas, 34% and 42% respectively, paid with a credit card. Suppose we select a customer at random.
a. Draw a tree diagram to represent this situation.
b. What is the probability that an automobile driver filled with regular gasoline AND paid with a credit card?
c. What is the probability that an automobile driver filled with premium gasoline AND did NOT pay with a credit card?
d. What’s the probability that the customer paid with a credit card?

Answer 1

Answer:

b) 0.2464

c) 0.0580

d) 0.2952

Step-by-step explanation:

Probability of those that purchased regular gas = 88% = 0.88

2% purchased mid grade gas

10% purchased premium gad

Given that a driver bought regular gas, 28% paid with credit card

Given that a driver bought mid grade gas, 34% paid with credit card

Given that a driver bought premium gas, 42% paid with credit card

Let R represent drivers that bought regular gas

Let M represent drivers that bought mid grade gas

Let P represent drivers that bought premium gas

Let C represent credit card payment

Let NC represent non-credit card payment

Pr(R) = 88% = 0.88

Pr(M) = 2% = 0.02

Pr(P) = 10% = 0.10

Pr(C|R) = 28%= 0.28

Pr(C|M) = 34%= 0.34

Pr(C|P) = 42%= 0.42

Pr(NC|R) = 1 - 0.28= 0.72

Pr(NC|M) = 1 - 0.34 = 0.66

Pr(NC|P) = 1 - 0.42 = 0.58

Using multiplication rule

Pr(AnB) = Pr(A) * Pr(B|A) = Pr(B) * Pr(A|B)

Using conditional probability,

P(B|A) = Pr(AnB) / Pr(A)

Pr(CnR) = Pr(R) * Pr(C|R)

= 0.88*0.28

= 0.2464

Pr(CnM) = Pr(M) * Pr(C|M)

= 0.02*0.34

= 0.0068

Pr(CnP) = Pr(P) * Pr(C|P)

= 0.10*0.42

= 0.0420

b) the probability that an automobile driver filled with regular gasoline AND paid with a credit card =

Pr(CnR)

= 0.2464

c) the probability that an automobile driver filled with premium gasoline AND did NOT pay with a credit card = Pr(P n NC) = Pr(NC|P) * Pr(P)

= 0.58 * 0.10

= 0.0580

d) The probability of those that paid with credit card is given as

Pr(CnR) + Pr(CnM) + Pr(CnP)

= 0.2464 + 0.0068 + 0.042

= 0.2952