00:01
So this is a one sample test inference around the mean.
00:05
And so we'll start out with our part a, writing our ho and our ha, our null hypothesis.
00:10
So our null hypothesis is going to be that mu is equal to 4 .5 minutes, because that's what we're comparing to.
00:20
He wants to determine that, and he wants to decide if that mean time has changed.
00:27
So my alternative is going to be a not equals to.
00:31
It just says changed, so we don't know if it's greater or less than.
00:35
So there's our null and our alternative.
00:38
As far as the critical value for an alpha 05, we'd want, since it's a two -tailed test, the not equals, this is 0 .025 on each end here, so it adds up to 5%.
00:51
And the critical value is on, it says it's a normal, approximately normally distributed, or it says it's normally distributed, so the critical value there is negative 1 .96.
01:00
You can look that up on a z table, or you can do an inverse normal button on a calculator for 0 .025.
01:08
And this critical value on this side is 1 .96...