list variables in the order of slowest varying to quickest varying

[athammad]

Hi,

I am trying to understand the meaning of the following sentence in the help of the function stratified:

Generally, if you are using more than one variable to create your "strata", you should list them in the order of slowest varying to quickest varying.

What is your definition of slowest and quickest varying?

[madamadami]

I've got the same question: just don't know what means slowest and quickest varying?