Which of the following is an example of a discrete variable?

• A. The height of a tree measured in $meters$
• B. The time taken to run a marathon
• C. The amount of rainfall in a day
• D. The number of students in a classroom

Answer: (D)

Verified step by step guidance

1. Understand the difference between discrete and continuous variables: A discrete variable is one that can take on only specific, separate values (often counts), while a continuous variable can take on any value within a range.
2. Analyze each option to determine if it represents countable values (discrete) or measurable values (continuous):
3. The height of a tree measured in meters is continuous because height can be any value within a range, including decimals.
4. The time taken to run a marathon is continuous because time can be measured with great precision and can take any value within an interval.
5. The amount of rainfall in a day is continuous because rainfall can be measured in fractions of units (like millimeters) and can take any value within a range.
6. The number of students in a classroom is discrete because students are counted in whole numbers and cannot be fractional.