Chapter 5, Problem 87H

Suppose that the useful life of a particular car battery, measured in months, decays with parameter 0.025. We are interested in the life of the battery.

a. Define the random variable. X =__________________________________

b. Is X continuous or discrete?

c. X $\sim$ ____

d. On average, how long would you expect one car battery to last?

e. On average, how long would you expect nine car barrettes to last. if they are used one after another?

f. Find the probability that a car battery lasts more than 36 months.

g. Seventy percent of the batteries last at least how long?