Any outcome can be assigned to one of four levels of measurement. Levels of measurement have an order, from the least precise being nominal to the most precise being ratio. The “higher up” the scale of measurement, the more precise the data being collected, and the more detailed and informative the data are. It may be enough to know that some people are rich and some poor (and that’s a nominal or categorical distinction), but it’s much better to know exactly how much money they make (ratio). We can always make the “rich” versus “poor” distinction if we want to once we have all the information.
...more
