Graphs are representations that point out numerical relationships or trends and include line graphs and bar graphs. Line graphs are useful for showing trends over time. For example, you could track the rising cost of tuition for colleges and universities in a persuasive speech about the need for more merit-based financial aid.
Bar graphs are good for comparing amounts. In the same speech, you could compare the tuition of two-year institutions to that of four-year institutions. Graphs help make numerical data more digestible for your audience and allow you to convey an important numerical trend visually and quickly without having to go into lengthy explanations. Remember to always clearly label your x-axis and y-axis and to explain the basics of your graph to your audience before you go into the specific data. If you use a graph that was created by someone else, make sure it is large and clear enough for the audience to read and that you cite the original source.
Source: National Center for Education Statistics, Fast Facts,http://www.nces.ed.gov.