00:01
For your problem, you want to see if there's evidence that the mean systolic blood pressure, they want to check and see is the mean systolic blood pressure for males higher than that for females.
00:12
And alternately, that would end up being our null, actually, would be that they're equal.
00:17
And this would be a two -sample t -test.
00:23
And these standard deviations are unknown.
00:27
That's an s.
00:29
And so the actual answer is you don't need to know what the, for your setting, your first response says it is not necessary to estimate the population variances for this test.
00:43
Well, i mean, you need to estimate them.
00:46
You need to have what they are.
00:48
So that's really not the best answer.
00:50
But you can pool them.
00:52
You can pool them together.
00:54
And the pooled standard deviation is to take one less than the sample size, which is that 31 times the variance of the first.
01:09
And the variance of the first, or the standard deviation, is 10 .2.
01:12
So we square it...