00:01
So they conducted a survey and found from their survey of not 49 people that the mean amount spent on smoking was $20 and a sample standard deviation of five.
00:11
And we want to give a point estimate to begin with, a point estimate for what the mean is.
00:20
And the point estimate is going to end up being our x bar.
00:24
So we would estimate with a single number or a point that $20 is probably what the money.
00:31
Mean is.
00:32
Now we know we're probably, it's probably not exactly 20, and that's why we want to find a confidence interval.
00:38
So let's determine a 95 % confidence interval for the mean.
00:42
So this is our point, single number estimate, and then we're going to get an interval estimate.
00:47
So we're going to take our x bar plus or minus our z value times that sample standard deviation over the square root of n.
00:54
And we know we can use this formula because we know n is greater than or equal to 30.
00:59
So even if this population distribution is not normal.
01:04
We're okay to use it because the sampling distribution would be approximately normal...