Issue on page /03.01-descriptives.html

[biomarkerman]

Just a small note: mad() was deprecated in pandas. Now, they'd like us to write the whole formula again

Ref: https://pandas.pydata.org/pandas-docs/version/1.5/reference/api/pandas.DataFrame.mad.html

[ethanweed]

Thanks for the heads up - I will try to re-write this section once the semester is underway!