Average daily time on a computer. Now you determine that it's impractical to go talk to everyone, so you're not going to be able to figure out the exact population parameter, average daily time on a computer, so instead you do a sample study. You randomly sample, and there's a lot of thought in thinking about whether your sample is truly random, so you randomly sample, but there's also different techniques of randomly sampling. So you randomly sample people from your population, and then you take the average daily time on a computer for your sample, and that is going to be an estimate for the population parameter. So that's your classic sample study. Now in an observational study, you're not trying to estimate a parameter, you're trying to understand how two parameters in a population might move together or not. So let's say that you have a population now.