Which of the following is a continuous random variable?

• A. Height in centimeters.
• B. The number of customers arriving in an hour.
• C. The number of pages in a book.
• D. The color of a car.

Answer: (A)

A continuous random variable can take any value within a range, including infinitely many values that can be distinguished with increasing precision. Height in centimeters fits this idea because, in theory, it can be measured to arbitrary precision (for example, 170 cm, 170.1 cm, 170.01 cm, and so on). The other options are discrete or qualitative: the number of customers arriving in an hour is a count and can only be whole numbers; the number of pages in a book is also a whole number; the color of a car is a category, not a numerical value.