Which is an example of a discrete variable?

• A. The amount of weight gained for each freshman at a local college
• B. The gender of each student in a psychology class
• C. The age of each student in a psychology class
• D. The amount of time to solve a problem

Answer: (B)

The main idea is distinguishing discrete versus continuous variables. A discrete variable takes on distinct, separate values, often categories or countable numbers, rather than a smooth range. Gender is a discrete variable because it represents a finite set of categories (such as male, female, nonbinary, etc.) rather than a measured amount on a continuous scale.

The other options involve quantities that can vary fluidly and take on many values within a range: weight gained can be any real number on a scale, age is measured as a precise value (often with months and days, not just whole numbers), and time to solve a problem is a continuous measure that can be expressed with fractions of a second. So gender stands out as the discrete example.