Two individuals are randomly selected from the 310 study participants with replacement. What is the probability that only one of them smokes? Among the smoking participants of this survey, there are proportionally more workers than teachers. Is it valid to draw a conclusion that certain occupation makes one more likely to smoke? If so, explain why. If not, suggest a confounding variable and explain how it explains the association between smoking and occupation. Suppose that in the population of all individuals having one of these four occupations, 8% are doctors, 13.5% are teachers and 61.5% are workers. It is also known that 15% of the population are smokers, and 20% of all engineers are smokers. An individual is randomly chosen from the population. Find the probability that the chosen individual is an engineer and that he/she does not smoke. Define your events and write down any probability rules that you used in your calculation.