Did high gas prices keep Americans from hitting the road this past summer? In a nationwide survey of adults, one variable measured was how many days vacationers spent driving on the road on their...

Did high gas prices keep Americans from hitting the road this past summer? In a nationwide survey of adults, one variable measured was how many days vacationers spent driving on the road on their longest trip. Consider the following (partial) probability distribution for the random variable X = the number of days for the longest car trip.

Value of X 4=.10, 5=.20 6=.25 7=? 8=?? Probability 0.10 0.20 0.25 ? ??

a) Suppose the probability of 7 days is twice as likely as the probability of 8 days. What are the two missing probabilities to complete the distribution for X?

b) Find the expected number of days for the longest car trip done last summer, E(X) and interpret.