So let's just think about what's going on here. Sunil might have some type of a null hypothesis. Maybe he got this 100, maybe he read a magazine article that says that on average, the average teenager sends 100 text messages per day. And so maybe the null hypothesis is that the mean amount of messages per day that he and his friends send, which was signified by mu, maybe the null is 100, that they're no different than all other teenagers, and maybe he suspects, and actually they say it right over here, his alternative hypothesis would be what he suspects, that they'd send more than 100 text messages per day. And so what he does is he takes a sample from the population of days, and there's over 365. They say they've been using the group messaging app for over a year. And he takes seven of those days.