00:01
So we're given a 90 % confidence interval, the last stop, for a population mean, and that interval is from 70 to 80, and this is going to be x bar plus or minus the margin of error, and this is based on a sample of 36 observations.
00:28
So our sample mean for part a is going to be the midpoint of that interval, which is x bar is equal to 75, so that is answer d.
00:42
And then for question b, calculate the margin of error.
00:46
Well, that is half the length of that confidence interval, so the margin of error is equal to 5, because the lower limit is 5 less than 75, and the upper limit is 5 greater than 75.
01:09
And then let's see here, that is answer a, b, c, d, so again d.
01:20
And then for question c, calculate the sample standard deviation.
01:25
Well, the margin of error is equal to z alpha over 2 times s over the square root of n, and we know what alpha is, that's 10%, the last stop...