00:01
So we have a scenario in which we're going to assume that the mean is equal to the 35 kilograms per square meter, and alternately that the mean is smaller than that, that they've been overestimating it.
00:13
And we get from our sample of 400, we have an x bar of 31 .75 and a standard deviation of 10 .5.
00:27
And we want to find out if we have evidence to show that it's lower at an alpha level of 1%.
00:33
And so those were our null hypotheses, our null and alternative hypotheses, and if we just quick draw a picture, we know we're assuming that 35 is our value, and we need to calculate the test statistic and find out if we have evidence to show that it is, and i don't assume, we're assuming that it's at the lower end, and it is coming in lower.
00:57
Let's find what that critical t value is.
01:00
I would like to have a t value with 399 degrees of freedom, that critical value here.
01:07
And at 1%, i don't actually have 399.
01:11
I have 100 degrees of freedom...