Four Levels of Measurements
Nominal: Objects are classified into simple attributable categories with no quantitative difference between them, (Yes/No, Good/Bad).
Ordinal: Objects are able to be arranged, ranked, or ordered into a meaningful attributable arrangement with no real measurement. (Yellow/Blue/Green, Square/Round/Triangle)
Interval: observations are able to be ranked into exact differences between any two observations, measurements with no natural origin or zero, 80 degrees is not twice as hot as 40 degrees. A one unit scale change corresponds to a one unit change on the o
Ratio: contains all the properties of interval but has a natural origin. Having a natural origin allows 25 to behalf of 50.
Note that each successive level has all the properties of the previous.