Why do graphs mislead?

Answer 1

Graphs can mislead people by the way they are prepared. See related links for good examples of misleading graphs. When you see a graph, you are seeing a summary of the data. Sometimes our data is misleading, so the graph is just presenting misleading data. For example, I show a graph of how much men and women make each year at a company. I see men make more every year, while women just stay about the same. Perhaps the company just has one woman working there. Perhaps in her job, there are no salary increases. I can also not start the y-axis at zero, to exagerrate the differences. A chart should include all the data. Excluding some data can result in a misleading graph. However, in a graph showing changes over period of time, the preparer of the graph has to chose how long a period is relavent. If we are explaining global warming, a plot showing 100 years might be good. But a graph of car accidents per year, perhaps 5 years is more reasonable.