Class variables are alternately called category, text, nominal, or string variables. They do not have numerical values. They are items or choices. For instance, “Which is better: a car, a motorcycle, or an airplane?” Here the DV is a method of transportation, and the assessment of best could be related to fuel and insurance cost, joy of travel, number of friends you can bring, operator training cost, speed of transportation, parking upon arrival, etc. The decision variable, the list of items, does not have a common, quantifiable metric (either continuum-valued or discretized) that defines the OF. In size, the airplane is largest and motorcycle smallest, but this aspect is not what defines the OF. The motorcycle might accelerate the fastest, and the car carries the most luggage per passenger, but, again, these are consequences of the DV.