Case Study 1
People with headaches are randomly divided into 2 groups. one group gets pain meds, another does not. An hour later participants are asked about pain.
This is a experiment. Control : No drugs Treatment : Drugs Effect : Whether the drugs work or not
Case Study 2
Researchers want to determine if smoking causes decreased lung capacity. they gather 2 random of 100 people. one group smokes a pack a day, while the other group does not smoke at all. after 2 years, the researchers assess lung capacity in both groups. (This is called a longitudinal study).
Theres some ethics involved in here. You should be using old smokers opposed to new addicts.