500
Yameak designs a new drug to improve hearing. He gives the drug to 50 participants, who have an average hearing level of 34. He gives a placebo to 50 other participants, who have an average hearing level of 40. After the experiment, the control group has an average hearing level of 39 and the experimental group has a level of 38. How much did each group's hearing level change by? AND did the drug work? Why or why not?
CG decreased by 1. EG increased by 4. Yes, the drug worked!