00:01
We have been given some sample data.
00:02
Sample size n is 15.
00:05
Sample mean x bar is 14 .8.
00:08
Sample standard deviation s is 0 .86.
00:11
We want a confidence interval for the population mean.
00:15
The formula for that is x bar, point estimate, plus and minus the margin of error, t s over root n.
00:23
So t is our critical value here.
00:24
We've been told to use t, but it's good to recognise that you should be using it, even if you were not told which one to use.
00:30
The other critical value that's an option is z.
00:33
We cannot use that because sigma, the population standard deviation, is unknown.
00:39
If i knew sigma instead of s, i'd be using z.
00:43
To get t we need three pieces of information.
00:46
First that we want the two -tailed value...