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Switch the Inner and Outer Categories on a Bar Chart

Did you just go shopping for school supplies? If you did, you’ve participated in what’s become the second biggest spending season of the year in the United States, according to the National Retail Federation (NRF). Kids running in backpacks

The trends and analysis are so interesting to the NRF that they actually add questions about back-to-school shopping to two monthly consumer surveys. The two surveys have different questions, but there’s one case where the allowed responses are the same. In July, the survey asked, “Where will you purchase back-to-school items this year?” In August, the survey asked, “Where do you anticipate you will do the remainder of your Back-to-School shopping?”

Did people give the same answers both times? Let’s use Minitab Statistical Software to find out. Doing so will give us a chance to see how easy it is to change the focus of a chart by switching the inner and outer categories on a bar chart.

Did people answer the same way in both surveys? Yes.

Let’s say that your data are in the same layout as the original NRF reports. Each row contains the percentage for a different location. I put the dates in two different columns because the numbers came from two different PDF files (July and August).

Percentages of people who said that they would shop at each location.

Making a bar chart in Minitab is easy, so follow along if you like:

  1. Choose Graph > Bar Chart.
  2. In Bars represent, select Values from a table.
  3. Under Two-way table, select Cluster. Click OK.
  4. In Graph variables, enter '7/1 to 7/8 2014' '8/5 to 8/12 2014'
  5. In Row labels, enter 'Where will you purchase?' Click OK.

From this display, you can quickly determine that the order of the categories is the same in each survey. In both cases, most consumers plan to shop the most at discount stores and the least from catalogs. In fact, the popularity of where consumers planned to shop and where they planned to finish shopping has a constant order.

With month outermost, you can see that the popularity of the categories is the same in both surveys.

Did people answer the same way in both surveys? No.

The order of popularity might not be all that you want to know from this data. Minitab makes it easy for you to get another view of the data. You can quickly switch which category is inner and which is the outer category.

  1. Press CTRL + E.
  2. In Table arrangement, select Rows are outermost categories and columns are innermost. Click OK.
  3. Double-click one of the bars in the graph.
  4. Select the Groups tab. Check Assign attributes by graph variables. Click OK.
  5. Double-click one of the category labels on the bottom of the graph.
  6. Select the Show tab. In the Show Labels By Scale Level table, uncheck Tick labels for Graph variables. Click OK.

With categories outermost, you can see which locations have the biggest change between the two surveys.

In this display, you can easily see the change for each location between the two questions. For every location, the number of people who reported that they planned to shop there on the first survey is higher than the number who planned to finish shopping there on the second survey.

This result seems reasonable. One possible explanation is that people finished their shopping at some locations. In terms of the difference in the percentages, those who plan to shop for school items at clothing stores and electronics stores changed the most. Customers who finished shopping at a location seem to have finished at those types of locations the earliest.

Wrap up

When you’re looking at data, discovering what’s important often involves looking at the data from more than one perspective. Fortunately, Minitab’s bar chart makes it easy for you to change the focus of the categories so that you can dig deeper, faster. It’s nice to know that the information that you need is so readily available!

Bonus

I set up my data as values from a table today. Want to see what the other two options do? Check out Choosing what the bars in your chart represent!

The image of the children running in backpacks is from healthinhandkelowna.blogspot.com and is licensed under this Creative Commons License.

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