You are in the process of assessing your firm’s online marketing strategy, and would like to know whether visitors to your Website who arrive from a search engine ad (after searching for your firm’s products) are more or are less likely to make a purchase than others. Focusing on all recent visitors, you have assembled the following information: 6% made a purchase, 27% arrived from a search engine ad, and 17% of those who made a purchase had arrived from a search engine ad. 

a. Draw a probability tree for this situation. 

b. Given that they arrived from a search engine ad, find the probability that they made a purchase. 

c. Given that they did not arrive from a search engine ad, find the probability that they made a purchase. 

d. Does it appear that visitors to your Web site who arrive from a search engine ad are more likely to make a purchase than others?