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. One way that they would be independent for sure is if Sunil is sampling with replacement. They don't say that, but another condition, so you either could have replacement, sampling with replacement, or another way where you could feel that it's roughly independent is if your sample size is less than or equal to 10% of the population. Now in this situation, he took seven, he took a sample size of seven, and then the population of days, it says that they've been using the group messaging app for over a year, so they've been using it for over 365 days.