69
4. Identify and discuss at least five (5) threats to internal validity in experimental designs.
Include in your answer ways of controlling for each of the threats you identify.
5. Give two (2) specific examples of research where a quasi-experimental design would be
more appropriate than a classical experiment. Why would each of your examples not fit
the classical experiment model?
6. Describe an experimental design to test the causal hypothesis that D.A.R.E. reduces drug
use. Is your experimental design feasible? Why or why not?
7. Experiments are often conducted in public health research where a distinction is made
between an efficacy experiment and an effectiveness experiment. Efficacy experiments
focus on whether a new health program works under ideal conditions; effectiveness
experiments test the program under typical conditions that health professionals encounter
in their day-to-day work. Discuss how efficacy experiments and effectiveness
experiments reflect concerns about internal validity threats on the one hand and
generalizability on the other.
8. Crime hot spots are areas where crime reports, calls for police service, or other measures
of crime are especially common. Police in departments with a good analytic capability
routinely identify hot spots and launch special tactics to reduce crime in these areas.
What kinds of validity threats should researchers be especially attentive to in studying the
effects of police interventions on hot spots?