Question

The following table gives the percentage of music downloaded from the United States and other countries by U.S. users: Country U.S. Germany Canada Italy U.K. France Japan Other Percent 45.2 16.4 6.5 6.3 4.2 3.7 2.1 15.6 (a) Verify that the table does give a probability distribution for the experiment. The sum of the percents is %, so this does give a probability distribution. (b) What is the probability that a U.S. user who downloads music, selected at random, obtained it from either the United States or Canada? (Enter your answer to three decimal places.) (c) What is the probability that a U.S. user who downloads music, selected at random, does not obtain it from Italy, the United Kingdom (U.K.), or France? (Enter your answer to three decimal places.)

Answer 1

A) 100%; B) 0.517; C) 0.858

Explanation:

For part A,

We find the sum of the probabilities:

45.2+16.4+6.5+6.3+4.2+3.7+2.1+15.6 = 100

Since they sum to 100%, this is a probability distribution.

For part B,

We add together the probabilities for the US and Canada:

45.2+6.5 = 51.7% = 51.7/100 = 0.517

For part C,

We first add together the probabilities for Italy, the UK and France:

6.3+4.2+3.7 = 14.2%

Next we subtract this from 100%:

100-14.2 = 85.8% = 85.8/100 = 0.858