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:

From the data in the two-way table, about what is the value of the correlation between whether an addict is infected with HIV and how often he or she injects drugs?

A) Small but positive, say, r = 0.2.
B) Quite large and positive, say, r = 0.8.
C) Very small, close to r = 0.
D) Small but negative, say, r = -0.2.
E) r makes no sense for these data.