So, let's again look at how we solved for the last confidence interval. We still
know that the true population mean, Mu sub BT, is going to be within 1.96
standard deviations of our sample mean. So, our sample mean is 40. And if we
subtract 1.96 standard deviations, we subtract 1.96 times 1.01. So this is
38.02, approximately. And then, to find the upper bound of this confidence
interval, we just add 1.96 standard deviations from the mean. So, this is about
41.98. It's pretty simple when we lay it out like this, just generically x bar
plus or minus the z score, in this case 1.96 since we want a 95% confidence
interval, times the standard deviation. But, really understanding the concept of
the confidence interval is really complicated. So, if you need to, keep
replaying these videos. Keep thinking about it. Don't worry. It took me a really
long time. I'm still completely understanding this stuff. It's complicated and
it requires some thought and patience.