Which of the following can be represented by a $discreterandomvariable$?

• A. The time it takes for a computer to complete a calculation
• B. The temperature measured to the nearest thousandth of a degree
• C. The exact height of a randomly selected student
• D. The number of $heads$ obtained when flipping a coin $3$ times

Answer: (D)

Verified step by step guidance

1. Understand the definition of a discrete random variable: it takes on countable values, often integers, such as counts or number of occurrences.
2. Analyze each option to determine if the possible outcomes form a countable set:
3. - Time to complete a calculation is continuous because it can take any value within an interval, not just countable values.
4. - Temperature measured to the nearest thousandth of a degree is still considered continuous because it can take many values within a range, even if rounded.
5. - Exact height of a student is continuous since height can vary continuously and is not restricted to countable values.
6. - Number of heads when flipping a coin three times is discrete because it can only be 0, 1, 2, or 3, which are countable outcomes.