Histogram

http://upload.wikimedia.org/wikipedia/commons/thumb/c/c3/Histogram_of_arrivals_per_minute.svg/250px-Histogram_of_arrivals_per_minute.svg.png

Histograms are designed to show distribution of data in a way that makes it easy for people to compare visually. This histogram shows the frequency and arrivals per minute. For example at 6 arrivals per minute there was a frequency of about a 6 or 7.