ABSTRACT
This chapter discusses two types of data—interval and ratio. Interval data improves on rank order data because with interval data the distance between levels is quantifiable and translatable. The Fahrenheit temperature scale is an interval scale. Going from 45 degrees Fahrenheit to 50 degrees Fahrenheit is the same interval as going from 53 degrees Fahrenheit to 58 degrees Fahrenheit. Ratio data improves on interval data because it adds in the idea that zero on the scale means total absence of the thing the scale is measuring. Many self-report scales in psychology are constructed so that the lowest possible score is five or ten or even seventeen. Zero degrees Fahrenheit is not the total absence of heat. There are negative temperatures below zero. The Beck Depression Inventory-II is a 21-item self-report depression inventory designed to assess symptoms and level of depression. The Satisfaction with Life Scale assesses an individual's global satisfaction with his or her life.
