In setting up experiments and formulating operational definitions, researchers also consider the available scales of measurement for each variable. You might have noticed that in our examples of independent variables, some of the levels we specified were simply comparative labels (bright or dim illumination, large versus small typeface). However, we could have indicated precise quantitative measurements, such as 50 versus 100 luxes (standard units of illumination) and 10-point versus 14-point typeface.