ONE COMMON USE OF GRAPHS IS TO COMPARE two sets of data. The comparisons may show a trend (time series) in one group, or a difference between two or more groups. 

Trend graphs show how something changes over time.

• Trends are often shown with a line or bar graph.
• The x or horizontal axis is always the time variable.
• Keep consistent time intervals. 
  

Often, one set of data needs to be compared to another set of data. For example, some schools like to compare themselves to the entire district or nation. These data comparisons can be shown through bar or line graphs, or pie charts. 

Bar and line graphs are the preferred depiction of data.

• Use a legend to clearly label what bars/lines mean.
• Keep a consistent scale.
• Keep consistent widths of the bars.

Pie charts are used predominantly to show percentages or parts of a whole.

• When comparing two separate sets of data, be sure to keep the colors consistent across pies.
• Include labels for each pie section.
  

Zannette Perry