00:01
For this problem, we are told that the claim is that the latest model can go at least 30 miles per gallon on average.
00:08
So that would mean that the average is greater than or equal to 30.
00:14
So that would, since there is a possibility of equality there, it could be that the mean is equal to 30, but it also might be more.
00:22
That will be our null hypothesis.
00:25
And our alternative hypothesis will be that the mean value is strictly less than 30.
00:29
So we can see that we are doing a left tail test.
00:34
Now we know that we have a sample of size 50, we have a sample mean or sample average of 28 .5, and a sample standard deviation of 4 miles.
00:48
Since our population standard deviation is unknown, but our sample size is sufficiently large for the central limit theorem to apply, n greater than 30, we can use the t distribution for testing this hypothesis.
01:02
So, since we're doing a left tail test at the 0 .01 significance level, we can declare our decision criteria.
01:12
I can't remember the proper phrase off the top of my head...