The Los Angeles Times reported that the US Postal Service is

The Los Angeles Times reported that the U.S. Postal Service is getting speedier, with higher overnight on-time delivery rates than in the past. The Price Waterhouse accounting firm conducted an independent audit by seeding the mail with letters and recording on-time delivery rates for these letters.

Suppose that the results were as follows (these numbers are fictitious but are compatible with summary values given in the article).

Use the given information to estimate the following probabilities.

(a) the probability of an on-time delivery in Los Angeles


(b) the probability of late delivery in Washington, D.C.


(c) the probability that two letters mailed in New York are both delivered on time


(d) the probability of on-time delivery nationwide

Solution