Polling. Professional polling organizations face the challenge of selecting a representative sample of U.S.

adults by telephone. This has been complicated by people who only use cell phones and by others whose landline phones are unlisted. A careful survey by Democracy Corps determined the following proportions:

Cell phone only 39%
Both cell and landline 29%
Landline only listed 22%
Landline only unlisted 7%

a) What’s the probability that a randomly selected U.S.
adult has a landline?

b) What’s the probability that a U.S. adult has a landline given that he or she has a cell phone?

c) Are having a cell phone and a landline independent?
Explain.

d) Are having a cell phone and a landline disjoint? Explain.