We're going to be dealing with a t distribution and a t statistic. With that said, let's think of it this way. We can come up with a t statistic that is based on these statistics right over here. The t statistic is going to be 17.17, our sample mean, minus the assumed population mean, minus 20 parts per million, over our sample standard deviation, 2.98. This is really the definition of the t statistic. Hopefully, we see now that this really comes from a z score. The t distribution is kind of an engineered version of the normal distribution using t statistics.