Statistics

Bar graphs look very much like histograms except that gaps are left between adjacent bars. This difference is based on the fact that bar graphs are usually used to represent discrete data and the space between bars is a reminder of the discrete character of the data represented.

Line graphs can also be used to represent continuous data. If one were to record the temperature once an hour all day long, a line graph could be constructed with the hours of day along the horizontal axis of the graph and the various temperatures along the vertical axis. The temperature found for each hour could then be plotted on the graph as a point and the points then connected with each other. The assumption of such a graph is that the temperature varied continuously between the observed readings and that those temperatures would fall along the continuous line drawn on the graph.

A circle graph, or "pie chart," can also be used to graph data. A circle graph shows how the total number of individuals, cases or events is divided up into various categories. For example, a circle graph showing the population of female African-Americans in the United States would be divided into pie-shaped segments, one (0-19) twice as large as the next two (20-20 and 30-39), and three about equal in size and smaller than the other three.