Based on analysis of data from last year, you have found that 40% of the people who came to your store had not been there before. While some just came to browse, 30% of people who came to your store actually bought something. However, of the people who had not been there before, only 20% bought something. You are thinking about these percentages as probabilities representing what will happen each time a person comes to your store.

a. What kind of probability numbers are these, in terms of where they come from?

b. Draw a probability tree for this situation.

c. Find the probability that a person coming to your store will have been there before and will make a purchase.

d. What is the probability that a customer had been there before given that the customer did not purchase anything during his or her visit?