Levels of measurement
Nominal data is classified without a natural order or rank.
Ordinal data is a type of categorical data with an order. The variables in
ordinal data are listed in an ordered manner. The ordinal variables are
usually numbered, so as to indicate the order of the list. However, the
numbers are not mathematically measured or determined but are
merely assigned as labels for opinions.
On the other hand, numerical or quantitative data will always be a
number that can be measured.