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. Let's say you have a population of 1,000 people. And you're curious about whether average daily time on a computer, how it relates to people's blood pressure. So average computer time, actually let me write it this way, instead of average computer time, it should just be computer time.