00:01
We have some sample data.
00:02
We want a confidence interval for the population mean.
00:05
Now, the formula for that is x bar, point estimate, sample mean, plus minus the margin of error, ts over root n.
00:16
T is our critical value because the population standard deviation is unknown.
00:21
We have not been given sigma.
00:24
Okay, so this is what we have, and we need each of these values.
00:33
Start with the descriptive statistics for the sample.
00:37
N the sample size.
00:38
Well, we have nine values here.
00:41
Sample mean and sample standard deviation.
00:44
You can get these by hands if you like, but it's very much busy work.
00:47
Feel free to use software or your calculator.
00:50
I'm going to be using my ti 84 with the one variable statistics option.
00:55
The sample mean is 11479 over 9.
01:01
That's the sum divided by 9.
01:05
Sample standard deviation.
01:07
The sum is equal to, okay, so it's 38 .7946 to four places, but i do have the exact value in my calculator.
01:20
Now for t, we need alpha over two and degrees of freedom...