And if you don't know what a placebo is, it's something that to the patient or to the person participating, it feels like they're taking something that you've told them might help them, but it does nothing. It could be just a sugar pill, just so it feels like medicine. The reason why you even go through the effort of giving them something is because oftentimes there's something called a placebo effect, where people get better just because they're being told that they're being given something that will make them better. So this could right here just be a sugar pill. And a very small amount of sugar, so it really can't affect their actual likelihood of getting the flu. So over here we have a table, and this is actually called a contingency table. And it has on it, in each group, the number that got sick, the number that didn't get sick.