﻿[Script Info] Title: [Events] Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text Dialogue: 0,0:00:00.32,0:00:04.86,Default,,0000,0000,0000,,So, let's again look at how we solved for the last confidence interval. We still Dialogue: 0,0:00:04.86,0:00:10.94,Default,,0000,0000,0000,,know that the true population mean, Mu sub BT, is going to be within 1.96 Dialogue: 0,0:00:10.94,0:00:18.19,Default,,0000,0000,0000,,standard deviations of our sample mean. So, our sample mean is 40. And if we Dialogue: 0,0:00:18.19,0:00:26.53,Default,,0000,0000,0000,,subtract 1.96 standard deviations, we subtract 1.96 times 1.01. So this is Dialogue: 0,0:00:26.53,0:00:33.04,Default,,0000,0000,0000,,38.02, approximately. And then, to find the upper bound of this confidence Dialogue: 0,0:00:33.04,0:00:39.44,Default,,0000,0000,0000,,interval, we just add 1.96 standard deviations from the mean. So, this is about Dialogue: 0,0:00:39.44,0:00:45.57,Default,,0000,0000,0000,,41.98. It's pretty simple when we lay it out like this, just generically x bar Dialogue: 0,0:00:45.57,0:00:50.97,Default,,0000,0000,0000,,plus or minus the z score, in this case 1.96 since we want a 95% confidence Dialogue: 0,0:00:50.97,0:00:56.78,Default,,0000,0000,0000,,interval, times the standard deviation. But, really understanding the concept of Dialogue: 0,0:00:56.78,0:01:01.43,Default,,0000,0000,0000,,the confidence interval is really complicated. So, if you need to, keep Dialogue: 0,0:01:01.43,0:01:06.30,Default,,0000,0000,0000,,replaying these videos. Keep thinking about it. Don't worry. It took me a really Dialogue: 0,0:01:06.30,0:01:11.58,Default,,0000,0000,0000,,long time. I'm still completely understanding this stuff. It's complicated and Dialogue: 0,0:01:11.58,0:01:14.67,Default,,0000,0000,0000,,it requires some thought and patience.