A colleague and I had a conversation about whether the following variables are categorical or quantitative.
1) Social security numbers
2) Phone numbers
3) Postal zip codes
We agreed that all three are in fact categorical, but couldn't agree on a good reason.
The definition of a categorical variable (at least here In statistics, a categorical variable is a variable that can take on one of a limited, and usually fixed, number of possible values, thus assigning each individual to a particular group or "category."
However, it seems a somewhat weak case can also be made that the variables are discrete valued random variables. I need one good reason to convince students of why these variables are not quantitative. Any ideas?