The mean is going to be 0. And we want to find an interval of t values between some negative value here and some positive value here that contains 95% of the probability. So this right here has to be 95%. And to figure what these critical t values are at this end and this end, we can just use a t table. And we're going to use the two-sided version of this because we're symmetric around the center. So you look at the two-sided. We want a 95% confidence interval.