Bill commutes to work in the business district of Boston. He takes the train 3/5 of the time and drives 2/5 of the time (when he visits clients). If he takes the train, then he gets home by 6:30 p.m. 83% of the time; if he drives, then he gets home by 6:30 p.m. 62% of the time. If Bill gets home by 6:30 p.m., what is the probability that he drove to work? (Round your answer to three decimal places.)

Respuesta :

Answer:

The probability that Bill drove to work given that he reached home by 6:30 PM is 0.3324.

Step-by-step explanation:

Denote the events as follows:

T = Bill takes the train to work

D = Bill drives to work

X = Bill gets home from work by 6:30 PM.

The information provided is:

P (T) = 0.60

P (D) = 0.40

P (X|T) = 0.83

P (X|D) = 0.62

The Bayes's theorem states that the conditional probability of an event Ei given that another event has already occurred is:

[tex]P(E_{i}|X)=\frac{P(X|E_{i})P(E_{i})}{\sum\limits^{n}_{i=1}P(X|E_{i})P(E_{i})}[/tex]

Use the Bayes' theorem to determine the value of P (D|X) as follows:

[tex]P(D|X)=\frac{P(X|D)P(D)}{P(X|D)P(D)+P(X|T)P(T)}=\frac{(0.62\times 0.40)}{(0.62\times 0.40)+(0.83\times 0.60)}=0.3324[/tex]

Thus, the probability that Bill drove to work given that he reached home by 6:30 PM is 0.3324.