Reading your Results Report - Histogram Graphs
Interpreting the results of the Graph - Histogram function
Now that you have created your histogram, it is time to interpret what it is telling you. When you created your histogram, a "chart" (your graph) was created, in addition to the data used to make the chart. These two pieces work together; if you change your data, the chart will also change.
You are provided with three options for creating a histogram - a pie chart, a bar chart, an area chart, or a 'Traditional Histogram'.
Pie Chart. A pie chart is relatively easy to interpret. The entire pie represents all possible values (except missing values) contained in the variable that you selected for the histogram analysis. Each slice of the pie represents the percentage of the total that each category contained in your data. In the "Legend" located on the right side of the pie chart, you will see what each slice of the pie represents. The only "problem" with pie charts is that they do not tell you how many people there were in each category (although you can show this in the Chart Options in Excel). (Glossary)
Bar Chart. A bar chart is also relatively easy to interpret. The bottom of the chart (called the X Axis) contains the categories or all possible values (except missing values) in the variable you selected for histogram analysis. The left side of the chart (called the Y Axis) contains the frequency of occurance - a simple count of how many times the specified value occurred. If your data sheet contains individual student data, the Y Axis will tell you how many students there were in each category. (Glossary)
Area Chart. An area chart is really nothing more than a fancy bar chart - it is interpreted precisely the same way.
Traditional Histogram. This type of graph can be interesting, and somewhat more complicated to interpret, because you can include more than one variable on the histogram. At its core, this type of graph is called 'traditional' because of the smooth line that connects the values along the X axis. You will see the various values of your chosen variable along the bottom (X axis), and the frequency count along the left side (Y axis).
To make your charts look prettier, please see the help topic associated with Modifying your graphs.