Levels of Measurement
Ratio measurement
Finally, in ratio measurement there is always an absolute zero that is meaningful. This means that you can construct a meaningful fraction (or ratio) with a ratio variable. Weight is a ratio variable. In applied social research most "count" variables are ratio, for example, the number of clients in past six months.
Interval measurement
In interval measurement the distance between attributes does have meaning. Example: when we measure temperature (in Fahrenheit), the distance from 30-40 is same as distance from 70-80. The interval between values is interpretable. Because of this, it makes sense to compute an average of an interval variable, where it doesn't make sense to do so for ordinal scales. But note that in interval measurement ratios don't make any sense - 80 degrees is not twice as hot as 40 degrees. (Distance is meaningful.)
Levels of measurement
It refers to the relationship among the values that are assigned to the attributes for a variable. Example: Party Affiliation=Variable YAP, Musavat, AXCP=Attributes 1, 2 , 3 = Values For purposes of analyzing the results of this variable, we arbitrarily assign the values 1, 2 and 3 to the three attributes. The level of measurement describes the relationship among these three values. In this case, we only use the values as a shorter name for the attribute.
Four levels of measurement
Nominal Ordinal Interval Ratio
Ordinal measurement
The attributes can be rank-ordered. Here, distances between attributes do not have any meaning. Example: On a survey you might code Educational Attainment as 0=less than H.S.; 1=some H.S.; 2=H.S. degree; 3=some college; 4=college degree; 5=post college. In this measure, higher numbers mean more education. But is distance from 0 to 1 same as 3 to 4? Of course not. The interval between values is not interpretable in an ordinal measure. (Attributes can be ordered.)
Nominal measurement
The numerical values just "name" the attribute uniquely. No ordering of the cases is implied. Example: jersey numbers in basketball are measures at the nominal level. A player with number 30 is not more of anything than a player with number 15, and is certainly not twice whatever number 15 is. (Attributes are only named, it is the weakest.)
