Are People More Emotional when Tired?

The best way to approach this question would be to conduct an experimental study. Only this method would allow us to make statements about what makes something happen; statements about what factor influences another. Any nonexperimental method would not permit us to explain if whether people are more emotional when tired.
A within subject design would be chosen to eliminate the differences between the two separate subject groups. Removing individual variance between subjects would greatly increase the validity of this experiment. …