1. Identify which one of the four types of validity--measurement validity, statistical conclusion validity, internal validity, or external validityis violated in each of the following scenarios. Explain your decision. (20 points)

a. In a longitudinal study ofexposure to formaldehyde and cancer, people from the Lower Ninth Ward who livedfor more than six months in a FEMA trailer following Hurricane Katrina werecompared to people whose homes were spared in the elegant Garden District ofNew Orleans.

b. Students were interviewed in agroup setting and asked questions about their attitudes toward dating and sex.

c. Citing a South African studythat found that circumcision reduced mens risk of contracting HIV by 45%, thehead of urology at a large Midwestern hospital encouraged his uncircumcisedpatients to undergo the procedure.

d. There were 10 fewer cases ofobesity for every 100 people who underwent the exercise intervention (95% CI:-0.25, 0.05).