Some variables, such as height, can be measured directly, and the measurement procedure is usually quite straightforward. Other variables—for example, hunger, motivation, or attitude about the death...

Some variables, such as height, can be measured directly, and the measurement procedure is usually quite straightforward. Other variables—for example, hunger, motivation, or attitude about the death penalty—are more difficult to measure.

Use the procedure you described in (a) to explain why there may not be a one-to-one relationship between a variable and the procedure used to measure it.