What are random variables in a simulation model?

• A. Fixed constants.
• B. Deterministic outputs.
• C. Only the input costs.
• D. Parameters that are not known with a high degree of certainty.

Answer: (D)

In a simulation model, random variables are the uncertain inputs that can take on different values according to a specified probability distribution. They are not fixed numbers, so they introduce variability into the model’s outcomes when you run many trials. They are not deterministic outputs, since the results change as these inputs vary. They aren’t limited to costs or any single category of input; they can represent any uncertain parameter in the system, such as demand, processing times, or arrival rates. The essence is that random variables embody uncertainty because their exact values aren’t known with high certainty, and that uncertainty is what you quantify and analyze through simulation.