Hi, could you tell me just based on this question why it would be a two factor ANOVA instead of a simple two population hypothesis testing question?

A random sample of people who work regular 9-5 hours and a random sample of people who work shifts were asked how many hours of sleep they get per day on average. An appropriate F-test was performed and it was found that the null hypothesis of the F-test should be rejected. Can we infer that there is a difference in the number of hours people sleep depending on whether they work 9-5 or shifts?