Bar Graphs and Histograms
Date: 04/30/2008 at 22:16:02 From: Michelle Subject: differences and similarities of bar graph vs. histogram What is the difference between a bar graph and a histogram? For example, what are some similarities or which bar graph explains more details. I'm confused about which graph touches with each other and how it shows details. Let's say 6 girls love dogs, 5 love cats, and 2 love hamsters, a bar graph would represent this data more than a histogram.
Date: 04/30/2008 at 23:31:48 From: Doctor Peterson Subject: Re: differences and similarities of bar graph vs. histogram Hi, Michelle. 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 - 3 pounds, 5 had pets weighing 3 - 6 pounds, and 2 had pets weighing 6 - 9 pounds, you could make a histogram of that. As a result of this difference, we make the bars of a histogram touch --that way, they illustrate the idea that they represent adjacent sets of numbers, and that together they cover an entire range of values. Discrete bar graphs represent separate entities, like your dogs, cats, and hamsters, and therefore are drawn separately, with space between. (Sometimes histograms are drawn with spaces, to indicate that they represent discrete numbers, that is, integers, rather than a continuous range of values. Also, sometimes at higher levels, the intervals can be different sizes, so the bars have different widths. Regular bar graphs always have the same width, because the width doesn't stand for anything in particular.) Also, the bars in a histogram ALWAYS represent frequencies (numbers of data values that fall in the corresponding interval); other bar graphs might represent other things such as the amount of money spent on different pets. (Actually, when bars can have different widths, it is not the height, but the area of each bar that represents the frequency.) There are some smaller differences relating to how they are drawn, such as how the bars are labeled, but these are the main ideas. See this page for a little more: Bar Graphs vs. Histograms http://mathforum.org/library/drmath/view/61175.html Here's an answer I found elsewhere: Math Central: Bar Graphs and Histograms http://mathcentral.uregina.ca/QQ/database/QQ.09.99/raeluck1.html This page explains a couple of the more advanced features I mentioned: Statistics Canada: Histograms and Histographs http://www.statcan.ca/english/edu/power/ch9/histograms/histo.htm If you have any further questions, feel free to write back. - Doctor Peterson, The Math Forum http://mathforum.org/dr.math/
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