A city manager has been given parking lot availability data. The data set provides parking spaces available every five minutes at parking lots (of all sizes, from small to very large) throughout the city. To assess the use of the parking lots in the city, the manager decides to take a sample from the large data set and find the sample mean number of lots taken. Explain why the sample mean is not a good summary to assess parking lot use throughout the city and recommend a more appropriate statistic.