Subject: double bar graphs

Name: Leslie

Who is asking: Parent
Level: Middle

My daughter has a homework problem in which she is graphing data from two frequency tables onto a double bar graph. The graph shows how many students worked in a program in two different years, grouped by age. In the first age group, one of the years has no students working, while there were students in that age group in the other year.

Does she simply graph the year with participants only, or is there some way to show that "zero" were in the other year? I can't seem to find that addressed anywhere!

Thank you!

Hi Leslie,

You certainly need to somehow indicate the "zero". There is no standard way to present a double bar graph or even a bar graph but I hope that my diagrams help.

First, if possible, I would present the graph so that it is clear there is something "missing". To be specific I would draw

rather than

In the first diagram it is clear that something is missing between the first two red bars.

I haven't put any labels on the diagram but you should label them. I expect that the text or the teacher have a prefered way to label the axes. Sometimes you see a number below each bar to indicate its height. If so you can put a "0" below the missing bar. Otherwise you may need a footnote. For example:

Footnote: In 1999 there were no students in the 8-12 year age group working in the program.

I am sorry that I can't be more specific as there is no standard way to present a bar graph.

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