00:01
For this problem, to begin, i'll note that we'll find our confidence interval by taking our sample mean value plus or minus the t -statistic for n -1 degrees of freedom, the tail proportion of, if we're looking for 95 % confidence, we want a one tail proportion of 0 .025, multiplied by our sample standard deviation divided by the square root of our sample size.
00:21
Now since we have a sample of size 11, that means that we have 10 degrees of freedom, and the critical t -value is going to be 2 .228.
00:31
So what i'll do is just set up my general formula here and then start plugging in the different values of s.
00:37
So to begin we know that s is equal to 25, so we'll set it up this way, i say s equals 25, then we'll have our lower bound, which will be 920 minus that t -value, 2 .228, times s, divided by the square root of 11, and then the upper bound is 920 plus 2 .228 times s, divided by the square root of 11...