When is the reference-class method appropriate for estimating task duration?

• A. For unique tasks.
• B. When there is no data at all.
• C. For similar tasks to leverage historical data.
• D. Only for repetitive tasks.

Answer: (C)

The reference-class method estimates how long a task will take by looking at past tasks that are similar in scope and complexity and using their actual durations to form an expectation for the current task. When you have a solid set of historical data from tasks that closely match what you’re planning, you can derive a realistic estimate and adjust for differences like constraints or team size. That’s why this approach is best described as appropriate for similar tasks to leverage historical data. It isn’t useful for unique tasks with no close analog, and it doesn’t require the task to be repetitive—what matters is finding a comparable reference class and applying its data.