1. 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.

• History-
• Experimental Mortality-
• Selection Biases-
• Testing-
• Maturation-

2. Give a specific example of research where a quasi-experimental design would be more appropriate than a classical experiment. Why would your example not fit the classical experiment model?

3. 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?

4. 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?