For a project, a student randomly picks 100 fellow AP Statistics students to survey whether each has either a PC or Apple at home (all students in the school have a home computer) and what score (1, 2, 3, 4, 5) each expects to earn on the AP exam. A chi-square test of independence results in a test statistic of 8. How many degrees of freedom are there?
1) 99
2) 7
3) 9
4) 4
5) 1