The Internal Revenue Service is studying the category of charitable contributions. A sample of 25 returns is selected from young couples between the ages of 20 and 35 who had an adjusted gross income of more than $100,000. Of these 25 returns, five had charitable contributions of more than $1,000. Four of these returns are selected for a comprehensive audit.
a. Explain why the hypergeometric distribution is appropriate.
b. What is the probability exactly one of the four audited had a charitable deduction of more than $1,000?
c. What is the probability at least one of the audited returns had a charitable contribution of more than $1,000?