Is it Observational Studies or Experimental Studies? Explain why.

(a) Twenty patients with migrants agree to be part of a study to test a new pain medication. They are split into 2 groups of 10 each randomly: one group gets the drug and the other group gets a placebo (looks exactly the same but does nothing). Neither doctors, administrators, or patients know which is which. All patients are instructed on how and when to take the drug and asked to record the percentage of pain relief that the pill gave them.

(b) ) In an attempt to study the health effects of air pollution, a group of researchers selected 6 cities in very different environments | some from an urban setting (e.g. greater Boston), some from a heavy industrial setting (e.g. eastern Ohio), some from a rural setting (e.g. Wisconsin). Altogether they selected 8000 subjects from the 6 cities and followed their health for the next 20 years. At this time their health prognoses were compared with measurements of air pollution in the 6 cities.