An investigator into the life expectancy of IV drug abusers divides a sample of patients into HIV-positive and HIV-negative groups. What type of data does this division constitute?

Nominal data (also known as nominal scale) is a type of data that is used to label variables without providing any quantitative value. Given question is about HIV-positive and HIV-negative groups; since there is no order of characteristic and it cannot be measured directly. So,it can't be an ordinal data or metric data respectively. It is nominal data as its division is based only on names, i.e. HIV-positive and HIV-negative groups.