1 00:00:00,320 --> 00:00:04,861 So, let's again look at how we solved for the last confidence interval. We still 2 00:00:04,861 --> 00:00:10,938 know that the true population mean, Mu sub BT, is going to be within 1.96 3 00:00:10,938 --> 00:00:18,192 standard deviations of our sample mean. So, our sample mean is 40. And if we 4 00:00:18,192 --> 00:00:26,528 subtract 1.96 standard deviations, we subtract 1.96 times 1.01. So this is 5 00:00:26,528 --> 00:00:33,039 38.02, approximately. And then, to find the upper bound of this confidence 6 00:00:33,039 --> 00:00:39,438 interval, we just add 1.96 standard deviations from the mean. So, this is about 7 00:00:39,438 --> 00:00:45,570 41.98. It's pretty simple when we lay it out like this, just generically x bar 8 00:00:45,570 --> 00:00:50,970 plus or minus the z score, in this case 1.96 since we want a 95% confidence 9 00:00:50,970 --> 00:00:56,780 interval, times the standard deviation. But, really understanding the concept of 10 00:00:56,780 --> 00:01:01,427 the confidence interval is really complicated. So, if you need to, keep 11 00:01:01,427 --> 00:01:06,305 replaying these videos. Keep thinking about it. Don't worry. It took me a really 12 00:01:06,305 --> 00:01:11,582 long time. I'm still completely understanding this stuff. It's complicated and 13 00:01:11,582 --> 00:01:14,673 it requires some thought and patience.