[ClaireW]

Hi, I’m trying to have students make bar graphs where the x-axis shows a categorical variable and the y-axis shows the mean of a numerical variable.  I know I can get the means to appear as lines over the points, but that’s not exactly a bar graph (and it doesn’t seem possible to change the y-axis to say “Mean of [variable]”).  Is there an easy way to do this that I’m missing?

[Bill Finzer]

Hi Claire,

It is possible to do. Once you’ve made a bar chart, go to the configuration menu as shown in the screen shot and choose Formula for the Scale. Then you can enter the formula you want and the bars’ heights will be equal to the result of evaluating that formula for each group of cases.

Hope that helps,

Bill

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   Roller-Coasters-CODAP.png
   

[ClaireW]

Hi Bill,

Thanks so much for the quick reply!  I’m not seeing that option unfortunately – see screenshot below.  I’ve confirmed that the x-axis variable is set to categorical and y-axis variable is set to numeric.  What am I doing wrong?

Thanks,

Claire

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   Screenshot-2025-07-12-at-12.41.20-PM.png
   

[Bill Finzer]

Hi Claire,

Ah, don’t put the numeric attribute on the y-axis. With the categorical attribute on the x-axis, choose Fuse dots into bars from the Configuration menu. Then, from that same menu, you’ll see the option to set the scale using a formula.

I just found the relevant page in the help system. I bet that will help! 😉

Bill

[ClaireW]

Ahh perfect, thank you, that’s exactly what I was missing!

One more quick question while we’re at it – I don’t suppose it’s possible to add error bars?

[Bill Finzer]

Sorry, you’re right. There’s no way to add error bars.

[Bill Finzer]

Hi again,

Just in case you aren’t already aware of the ability to show standard errors, check out the enclosed screen capture. Note that hovering over one of the error bars or its label causes lines to extend that make it easy to check for intersections with other error bars.

I know this doesn’t take the place of error bars associated with a bar chart. But maybe it’s better?

Bill

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   Standard-Errors.png
   

[ClaireW]

Good to know, thanks – not sure this quite works for my current purposes, but good for the students to play with.  Adding error bars to bar charts would be a great feature to consider for the future.

Thanks again for all your help!

[Author]

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