Graphical Statistics

3-D Line Graphing of the Energy Consumption Data

Three-dimensional graphs are used to show the relationship between two or more independent variables and one dependent variable. The data for this activity was obtained from the Greenwood Partnership, an architectural and engineering firm located in Lynchburg, Virginia.

The best way to visually represent data with three variables (one dependent and two independent) is a three-dimensional graph. Three dimensional graphs have three axes, the x, y, and z. In most cases the dependent variable is plotted on the y axis, and the independent variables are plotted on the x and z axes. This activity is a follow up to the 2-D Energy Consumption Activity, where the dependent variable, energy consumption, is plotted against the independent variable, time. It is recommended that you complete the 2-D activity prior to beginning this one.

This activity introduces a second independent variable, the type of use. We will be graphing the energy used for heating in addition to the energy used for cooling in the hospital. We will still plot degree-days on the y axis and time on the x axis like we did in the 2-D activity. However, now we add the new independent variable, type of use, to the graph by plotting it on the z axis. What do you think the new graph will look like compared to the graph you created for the 2-D activity?

Using Excel (the TI-83 is not capable of producing 3-D graphs), generate a 3-D line graph of the energy consumed over time, for both the heating and cooling data. Then answer the questions at the end of this page. The data exists in two files; one is Excel Data format and one is Text format.

Are there any patterns or trends that are present in the graph? What could be an explanation for these trends? Does the hospital use more heating or cooling? Why? What is the maximum amount of degree days of heating? of cooling?

Original work on this document was done by Central Virginia Governor's School students Patrick Burke, Rebecca Mispel, and Jialu Li (Class of '99).