In 1993, one of the first studies aimed at preventing maternal transmission of AIDS to infants gave the drug AZT to pregnant, HIV-infected women. Roughly half of the women were randomly assigned to receive the drug AZT and the others received a placebo. The HIV-infection status was then determined for 363 babies, 180 from the AZT group and 183 from the placebo group. Of the 180 babies whose mothers had received AZT, 13 were HIV-infected, compared to 40 of the 183 babies in the placebo group. Identify and classify the explanatory and response variables in this study
Explanatory: type:

Response: type: