Average Number of Books Purchased

A local bookstore conducted a survey to determine the average number of books purchased by customers in a month. The data collected showed the following number of books purchased by fifteen customers: 0, 1, 2, 2, 3, 3, 3, 4, 4, 5, 5, 6, 6, 7, 8.

What is the average (mean) number of books purchased by these fifteen customers?