00:01
So we're performing a two sample t test.
00:05
And we are assuming that the two means are equal and alternately that they are different.
00:14
So it is a two sample t test that is two -tailed.
00:18
And our test statistic, our t value, will end up being the difference between the two means.
00:24
So 15 .3 minus 18 .4.
00:28
I'm not doing any pooling of the standard deviations.
00:32
And so we're going to take the standard deviation of the first group, which is pretty big, divided by the sample size.
00:39
And the standard deviation of the second group, 14 .3 squared, divided by the sample size.
00:45
And if we were figuring out the degrees of freedom conservatively, we take the smaller sample size less one and say 79.
00:56
We're going to use the formula that the calculator is pre -programmed to calculate.
01:02
And also, some people will have in your textbooks that if each of these sample size is greater than or equal to 30, to go ahead and use a z value.
01:12
And so to figure out the value and use it as a z rather than a t.
01:21
And so let's see what we get here.
01:24
We find out that the test statistic is negative, naturally, 1 .1 .4.
01:29
I don't think you need four dozen places, but i'll give you another one.
01:34
And the value that the formula gives me is degrees of freedom of 150 .7...