And you have seen this before when we did significance tests with proportions. Here we're doing it with means, population mean, sample mean. In the past, we did it with population proportion and sample proportion. Well, the random condition, it says it right here, Sunil takes a random sample of seven days from their chat history. They don't say how he did it, but we'll just take their word for it that it was a random sample. The next condition is sometimes known as the independence, independence condition. And that's that the individual observations in our sample are roughly independent.