00:02
To calculate these confidence intervals, we're going to be using this formula involving z because we know the population standard deviation sigma.
00:10
Let's start with the 90 % confidence interval.
00:14
The sample mean x bar is 32.
00:17
Z at 90 % confidence is 1 .645.
00:22
We know sigma is 6, and our sample size was 50.
00:29
So the first thing i'm going to do is get our standard error.
00:32
6 divided by the square root of 50 makes 0 .8485.
00:42
And now we're going to multiply that by 1 .645 to get our margin of error for our interval.
00:53
And that's going to come out to be 1 .3958.
00:59
And now lastly, to get the endpoints of our 90 % confidence interval, i'm going to do 32 minus 1 .3958 and 32 plus 1 .3958, which on the low end is 30 .6042, and on the high end, 33 .3958...