A student is analyzing different types of variables in a statistics class. Which of the following below is a discrete random variable?

• A. The time it takes for a randomly selected runner to complete a 5k race
• B. The weight of a randomly chosen bag of apples from a grocery store
• C. The number of defective lightbulbs from a randomly chosen batch in a factory
• D. The number of days in a random month

Answer: (C)

Verified step by step guidance

1. Understand the definition of a discrete random variable: A discrete random variable is one that can take on a countable number of distinct values. These values are often whole numbers.
2. Analyze the options given: Consider each option and determine if the variable can take on a countable number of distinct values.
3. Option 1: 'The time it takes for a randomly selected runner to complete a 5k race' - Time is a continuous variable because it can take on any value within a range.
4. Option 2: 'The weight of a randomly chosen bag of apples from a grocery store' - Weight is also a continuous variable as it can take any value within a range.
5. Option 3: 'The number of defective lightbulbs from a randomly chosen batch in a factory' - This is a discrete random variable because the number of defective lightbulbs can be counted and is a whole number.