Research indicates that punishment:

is more effective if reinforcement for the target behavior is withheld or delivered infrequently

Explanation:

When the reinforcement is delivered frequently, people who misbehaved already make mental preparation to receive it. This will reduce the severity of the reinforcement over time.

If it's delivered infrequently, there will be added pressure from speculation whether the reinforcement will be delivered. This will make them become less likely to misbehave.

answer; (73%);

answer; rational if melanie values sleep more highly than the benefits she expects to receive from attending the class;