In a survey of 3000 high school seniors, 60% indicated that they used alcohol “on a regular basis,” while 40% did not. Forty-fve percent of the students who used alcohol regularly said they had experimented with drugs. Fifteen percent of the students in the survey who did not use alcohol regularly said that they had experimented with drugs.
a. What percentage of the students experimented with drugs?
b. What’s the probability of regular alcohol use given that a student experimented with drugs?
c. Are regular alcohol use and experimentation with drugs statistically independent? Explain.