Answer:
When referring to the age of subjects in a study, you are working with a quantitative variable. A quantitative variable is a type of variable that can be measured numerically and is often used to describe a characteristic or attribute of a population. Age is an example of a quantitative variable because it can be measured numerically in units such as years, and it can be used to describe the characteristics of a population, such as the age distribution of a study sample.
On the other hand, a qualitative variable is a type of variable that is non-numerical and is often used to describe a characteristic or attribute that cannot be measured numerically. Examples of qualitative variables include things like gender, race, and occupation, which can be described by categories or labels, but not by numerical measurements.