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Bar Graph vs. Histogram

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I want to talk about the difference between a bar graph and a histogram. Now, we’ve talked a little bit about histograms already. Say I have a number of different ages in some data set, and I want to look at how often each age occurs. Here, I’ve got a histogram like that on the screen. In this data set, I’ve got a number of 30-year-olds and people close to 30. Histograms make sense when a variable is continuous. I’ve got a range of age scores from, in this example, about 20 to 70. And then I can look at how often each age occurs.
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Because that variable is continuous– I can have a number of different values all the way up and down that age variable– I make my bars touch. And that is an important feature of a histogram. The bars cling together. They touch each other. And in fact, I could change the bar width and a whole number of different features. But the bars are always going to touch in a histogram.
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What is a bar graph, then? A bar graph looks like this. It looks really similar. But in the bar graph, the variable on that x-axis represents categories. We say it’s discrete. They represent groups or discrete or categorical values. So these are going to be things like your nominal variables and your ordinal variables. For instance, maybe I look at the frequency of males and females in my data set. In this case, there’s no continuous variable. So my bars are not going to touch. They represent discrete or separate groups. People often get bar graphs and histograms confused. But really, when you think about it, it makes sense. If the variable is continuous, my bars are going to touch– histogram.
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If the variables are categories, I’m going to keep them separate– bar graph.

Lesson 4: Bar Graphs and Pie Charts

This lesson throws a couple new types of data visualization into the mix: bar graphs and pie charts. We’ll see why bar graphs are more useful than histograms for certain types of data, and we’ll explore why bar graphs are way, way better than pie charts.

Lab: Bar Graphs and Pie Charts

In this lab, we’ll take another look at the coffee data set from previous labs, examine some of the categorical data it contains, and explore the difference between categorical and numerical data. We’ll also add a couple more data visualizations to our toolbelt: pie charts and bar graphs.

The lab instructions can be downloaded as a PDF file here.

The data set for this lab can be viewed here. From the link, copy and paste all the data into a new worksheet in Excel Online.

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Essential Mathematics for Data Analysis in Microsoft Excel

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