341: Sensible or Not? Study Types

Defend your answer! Here's your claim ... what's your warrant?
Give an example or a situation to bolster your position  

1. The Department of Education conducted an observational study to determine the average salary of high school teachers in each of the United States 
2. A paint company conducted a double-blind experiment to determine which of two types of exterior paint was more resistant to rain. 
3. The lab conducted an experiment to determine whether the throat culture was positive for strep. 
4. In a study of medications designed to slow the rate of balding in men, a placebo group had better results than the control group. 
5. A meta-analysis was conducted to determine the population of New Zealand. 
6. A case-control experiment was used to determine the average family size in Utah.