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Data Literacy Project
DL SPSeries: 10.19.11
Bar Graphs and Histograms: similarities and differences A helpful description from Dr. Math [http://mathforum.org/dr.math/ ] Questioner: “I'm confused about which graph has bars that touch on the sides, and which has bars that are separate. Let's say 6 girls love dogs, 5 love cats, and 2 love hamsters. A bar graph would represent this data better than a histogram, right?” Dr. Math replies: A histogram is a KIND of bar graph; so everything that a bar graph is, a histogram is too. But there are special things about a histogram that are not true of ordinary bar graphs, and these are the differences. One big difference is what they are used for. A bar graph can be used to compare ANY group of numbers, as in your example of the numbers who like different kinds of pets. That is very much like the sort of frequency distribution that histograms display, since you are graphing "frequencies"; but the bars would represent categories, not numbers.
A histogram is used ONLY when the bars will represent different numbers or intervals along an axis. For example, if 6 girls had pets weighing 0 -‐
DL SPSeries: 10.19.11
Bar Graphs and Histograms: similarities and differences A helpful description from Dr. Math [http://mathforum.org/dr.math/ ] Questioner: “I'm confused about which graph has bars that touch on the sides, and which has bars that are separate. Let's say 6 girls love dogs, 5 love cats, and 2 love hamsters. A bar graph would represent this data better than a histogram, right?” Dr. Math replies: A histogram is a KIND of bar graph; so everything that a bar graph is, a histogram is too. But there are special things about a histogram that are not true of ordinary bar graphs, and these are the differences. One big difference is what they are used for. A bar graph can be used to compare ANY group of numbers, as in your example of the numbers who like different kinds of pets. That is very much like the sort of frequency distribution that histograms display, since you are graphing "frequencies"; but the bars would represent categories, not numbers.
A histogram is used ONLY when the bars will represent different numbers or intervals along an axis. For example, if 6 girls had pets weighing 0 -‐