I want to start with some data and a model from outside biology. The “data” (such as it is) comes from a Dilbert cartoon, and the competing hypotheses about the data come from Dilbert (the hard-working and long-suffering engineer) and his boss (the evil pointy-haired boss). We will work through a statistical test to show that Dilbert is right and the boss is wrong — of course!
In this cartoon, Dilbert’s evil pointy-haired boss decides he’s found a new way that employees are cheating him: they are taking fake “sick days” on Mondays and Fridays in order to get longer weekends. His proof? The fact that 40% of sick days fall on a Monday or Friday.
Before we get into statistics, take a moment to think about the situation…
What proportion of sick days ‘should’ fall on Monday or Friday (assuming there is no bias to when people get sick, and no one is abusing their sick days?)