Which of the following statements about variables is NOT true?

- An individual can often be described with respect to many different variables.
- Two different individuals can be measured or described on the same variable, but the value or description of the variable may not be the same for both individuals.
- For one specific individual, the value of a quantitative variable may change over time but the value of a categorical variable will remain constant.
- The individuals in a sample should all be the same with respect to the variable that makes them part of a population of interest.