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Is there an online tool to generate Empirical Rule (68% / 95% / 99.7% ) graphs?

For example, to help with these Khan Academy exercises:

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If you find yourself needing a grapher here, you are missing the point of the exercise.

It looks like all of the questions are set up to ask about probabilities being either 1, 2 or 3 standard deviations from the mean.

As long as you know that 68% is within 1 deviation of the mean, and 95% is within 2 standard deviations, and 97% is within 3 standard deviations, and that the bell curve is symmetrical about the mean, you can always do these problems with a shoddy sketch of a normal curve on a napkin.

It's true that one could ask harder questions about values that fall somewhere other than these 6 convenient values, but then you would need a table (or tech) to look things up. Usually in texts (and I believe at that link) they are just trying to ramp you up to understand this most basic case.

I didn't look at every single exercise, so there could be one that is not one of these types. If so, please make comments below.

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