Graphs can be useful in making comparisons clearer. We have to be careful in reading graphs, for they can mislead or conceal claims by not not taking the base of the comparison to be zero, or by using bars, or by spacing the numbers on the axes in certian ways.
Missing Zero
Changing the range of scale on the vertical axis clearly distorts the relative lengths of bars in a bar graph, the shape of line in a line graph, or the shape of the "dot cloud" in the scatter plot.
Review the two examples linked below, which compare FCAT-Math scores from some schools. In the "small range" example, the vertical axis range is only from 299 to 306, a difference in score of 7 points. The relatively small differences in scores among schools are exaggerated in the bar graph because of the small range chosen for the vertical axis. Contrast this to the "correct range" example, in which the vertical axis starts at zero and ends at 300. The relative differences in scores among schools are more accurately displayed in this graph because of the correct choice of the scale.
Distorted Graph: Too Small Range/Vertical Axis Starts at 299
http://www2.fiu.edu/~graphing/distortedgraph.htm
V.S
Accurate Graph: Correct Range/Vertical Axis Starts at Zero
http://www2.fiu.edu/~graphing/correctrangemislead.htm
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Using graphs is a great way to make things clearer for some people, I do agree on that. But it does depends on, if the graph is done correctly, or the numbers in the graph is not exaggerated. Also, like you have said in your post, it depends on the graph itself too, the type of graph. Also, graphs are formed from data, that is taken by surveys or statistical data, that could be off a little. It would not be exactly accurate. Your blog regarding the graph is very informational, and I also like how you had given us a visual comparison of the graphs. Great way for people to understand.
ReplyDeleteYeah, I see this a lot online! I mean if you cannot find a distinct point on the graph for what you are looking for than it is basically useless for proving whatever point the graph was meant to support. It should be true to scale and labeled appropriately so as not to mislead those who are reading it. You bring up a really good point because people often get confused when presenting graphs for their evidence. Two times zero is still zero is a super common concept I see come up in a lot of papers and blogs. I think people mostly do it to manipulate other's opinion; but sometimes it is completely innocent, and they just do it because they have no idea what a graph is supposed to look like.
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