A Study of Drug Addicts in Amsterdam Recorded How Often

Multiple Choice

A study of drug addicts in Amsterdam recorded how often each addict had recently injected drugs and whether or not the addict was infected with HIV, the virus that causes AIDS. Here is a two-way table of the numbers of addicts in each condition:

The chi-square statistic for this table has how many degrees of freedom?

A) 1
B) 2
C) 3
D) 4
E) 6