00:01
So we have another hypothesis test and this one is going to end up being a t test.
00:06
It's a test for means.
00:07
And we have a sample size of 43 physics final exams which yielded a mean of 81 points with a standard deviation of 3 points.
00:17
And we want to do a test at a 2 % significance level.
00:21
And the claim is that the mean is higher than 78.
00:27
So your null hypothesis would be that the mean is equal to 78.
00:33
You could have it be less than or equal depending on, i have my students use this and just go equality.
00:40
But you could have less than or equal to as your null hypothesis.
00:46
But the claim is the alternative.
00:48
Now this will be a one -tail test.
00:51
And it's going to be a right -tail test.
00:54
I'm not going to go through all of your alternatives there.
00:58
But it's going to be a right -tail test because this alternative hypothesis or what they're claiming is strictly greater than.
01:05
So it's going to be a right -tail test.
01:07
So why don't we right now find the critical value? the critical value needs to have .02 in that upper tail.
01:16
And so we need to find this t value.
01:20
And the t value we have a sample size of 43.
01:24
So we would have 42 degrees of freedom.
01:28
And so we want to find that critical value.
01:30
And let me look and see if i have that in my chart.
01:34
And i do.
01:36
Forty, i have to quick look.
01:40
Is it 43 or 42? 42.
01:43
And so for 42 with 2, let me find the right column here.
01:50
I'm using a table online...