Now, we know from many other videos that you might not know the population parameter or it might not even be easy to find. And so the way that we try to estimate a population parameter is by taking a sample. So this right over here is a sample of size n, sample of size n. And then we can calculate a statistic from that sample, based on that sample, maybe we picked n balls from there. And so from that, we can calculate a statistic that is used to estimate this parameter. But we know that this is a random sample right over here. So every time we take a sample, the statistic that we calculate for that sample is not necessarily going to be the same as the population parameter. In fact, if we were to take a random sample of size n again and then we were to calculate the statistic again, we could very well get a different value.