given this example i need to find the following.

In the population, the average IQ is 100. A team of experimenters wants to test a new pill to see if it either has a positive or negative effect on intelligence, or not effect at all. A sample of 30 participants who have taken the pill has a mean of 140 with a standard deviation of 20. Did the pill affect intelligence? Lets say a= 0.05

Question: Identify the independent and dependent variables and at least one potentially confounding variable. State how the confounding variable(s) might be controlled.