In: Statistics and Probability
Consider the following statistical study and: a) Identify the population and the population parameter of interest. b) Describe the sample and sample statistic for the study. c) Identify the type of study. d) Discuss what additional facts you would like to know before you believed the study or acted on the results of the study. A study done at the Center for AIDS and STD at the University of Washington tracked the survival rates of 17,517 asymptomatic North American patients with HIV who started drug therapy at different points in the progression of the infection. It was discovered that asymptomatic patients who postponed antiretroviral treatment until their disease was more advanced faced a higher risk of dying than those who had initiated drug treatment earlier (New England Journal of Medicine).
(a)
the population : Asymptomatic North American patients with HIV
the population parameter of interest.: Survival rates of all asymptomatic patients with HIV
(b)
the sample : 17,517 asymptomatic North American patients with HIV
sample statistic for the study : The survival rates of 17,517 asymptomatic North American patients with HIV who started drug therapy at different points in the progression of the infection.
(c)
The type of study : Observational Study,
because the researcher does not manipulate the independent variable : here initiation of drug treatment earlier or later to study its effect on the dependent variable:here risk of dying , but simply records the details.
(d)
Additional facts you would like to know before you believed the study or acted on the results of the study.
Other than initiation of drug treatment earlier or later is not the only factor affecting risk of dying.There are a number of Confounding Factors such as life circumstances, legal and social factors. So, while recording the details of initiation of drug treatment earlier or later and survival rates of asymptomatic patients with HIV, the researcher should see that the confounding variables are controlled so that the final conclusion is attributed to drug treatment alone.