Chapter 1, Problem 60CRE

HIV-1 and HIV-2 Does infection with HIV-2 slow the progression to AIDS for those with HIV-1? A blood test is used to determine whether a person is infected with HIV. If a person has AIDS, it means the person is experiencing symptoms that result from the HIV infection. (It is possible to be infected with HIV and not show symptoms.) Read the extract given, and then answer the questions that follow it.

Methods We analyzed data from 223 participants who were infected with HIV-1 after enrollment (with either HIV-1 infection alone or HIV-1 and HIV-2 infection) in a cohort with a long follow-up duration (approximately 20 years), according to whether HIV-2 infection occurred first and the time to the development of AIDS (time to AIDS) ….

Result The median time to AIDS was 104 months in participants with dual infection and 68 months in participants infected with HIV-1 only…. Participants with dual infection with HIV-2 infection preceding HIV-1 infection had the longest time to AIDS….

a. Identify the treatment variable and the response variable.

b. Was this a controlled experiment or an observational study? Explain.

c. What do the median times to AIDS show, descriptively?

d. Can you conclude that the presence of HIV-2 slows the progression of HIV to AIDS? Why not?