00:01
For this problem, we know that we have a sample of 10 waterways.
00:05
We have a known population standard deviation, sigma, equal to 44 .73.
00:14
And we're looking to construct a 79 % confidence interval.
00:21
So, since we have a known population standard deviation, we can construct our confidence interval by taking x bar plus or minus the z score for...
00:29
Let's see here.
00:30
We first need to find our alpha, or level of significance, which is going to be 1 minus 0 .79.
00:37
That's going to be equal to 0 .21.
00:40
We want that tail proportion for our z score to be alpha over 2.
00:45
So 0 .21 over 2 is going to be 0 .105.
00:53
We multiply that by our population standard deviation, and then divide the result by the square root of the sample size.
01:01
So, to find that z score, i'll go to a cumulative distribution table...