The properties of the abstract number system that are relevant to scale of measurement are identity, magnitude, equal interval, and absolute/true zero.

• Identity means that each number has a particular meaning.
  
  
• Magnitude means that numbers have an inherent order from smaller to larger.
  
  
• Equal intervals means that the differences between numbers (units) anywhere on the scale are the same (e.g., the difference between 4 and 5 is the same as the difference between 76 and 77).
  
  
• Absolute/true zero means that the zero point represents the absence of the property being measured (e.g., no money, no behavior, none correct).

Now let's try some examples. Select either examples of levels of measurement you may encounter in everyday life or those typically found in psychological research.