Which of the following is true of the trends in infant mortality rate and life expectancy in the United States over the past century?
A) Infant mortality rates have increased and average life expectancy has decreased.
B) Infant mortality rates have decreased and average life expectancy has increased.
C) Both have decreased.
D) Both have increased.
Question 2
In the context of intervention studies, when researchers know who is in the treatment group and who is in the placebo group but participants do not, the study is called a(n) _____.
A) cohort study
B) single-blind study
C) double-blind study
D) epidemiologic study