Misleading Graphs

All Good Graphs Should … Include: 1.Title 2.Labels on both axes 3.Consistent Scale count by the same number each time!count by the same number each time! 4.Start at the origin That means start counting at zero!That means start counting at zero! 5.Make sure the scale is appropriate for the data! Data should take up most of the graph (not a lot of blank space)Data should take up most of the graph (not a lot of blank space)

Why learn about this? Graphs and statistics are often used to persuade. Advertisers and others may accidentally or intentionally present information in a misleading way.

This is a GOOD graph 1 st Quarter QT Results by Indicator Indicators Percent Mastery

This is a BAD graph

Graphs should not have breaks! Because the scale leaves out 0 to 100, the bar heights make it appear that the sixth grade sold about three times as many tickets as either of the other two grades. In fact, the sixth grade sold only about 20% more.

Don’t compress the scale! The scale is so compressed that it’s hard to see any difference among the brands.

Misleading Representations Bias a particular tendency or inclination, esp. one that prevents unprejudiced consideration of a question; prejudice. Statistics. a systematic as opposed to a random distortion of a statistic as a result of sampling procedure. Propaganda information, ideas, or rumors deliberately spread widely to help or harm a person, group, movement, institution, nation, etc.

Misleading Representations Are created and used to emphasize a specific point. Be a careful consumer of information: Read graphs carefully Note anything that parts of a GOOD graph that are missing! Think about what the ‘author’s purpose’ might be!

Why is this graph misleading?

This graph shows the same information…

What is the difference between them?

What is wrong with this graph? How would you fix it?

What’s wrong? The graph appears to indicate that significantly more people prefer grape drink over the others when in fact there is a small margin of difference. (0 to 140 is not graphed) Preferred Juice Flavors GrapeCherryApple

What’s wrong? This graph is too compressed to see much difference between the brands indicating that they are fairly equal Brand XBrand YBrand Z

Which one is misleading?

Compare and Contrast! Graph #1 Graph #2 Which is the more unbiased representation?

Homework Create your own bar or line graph with a scale that is inappropriate for 1 reason: Does not start at zero Does not change by the same amount each time Does not ensure that the data takes up most of the field. Explain, in complete sentences, why the scale makes the graph misleading!

Extra Credit! Find a chart or graph in a publication that displays data incorrectly! Should be from a newspaper or magazine or reputable website (i.e. Kansas City Star, CNN.com)