00:03
All right, welcome to numerade.
00:04
We need to do a significance test at the 0 .05 level of wait time for taxpayers to call the irs's helpline.
00:14
All right, so first thing we need to do is identify all the information that is given to us.
00:19
All right, so we are told that on average, the mean wait time for callers is 13 minutes.
00:28
Okay, then we are told that they take a sample of 50 callers.
00:34
So we know that our sample size is 50.
00:38
We are told that our sample size mean is 11 minute wait time.
00:45
And we are told that the standard deviation is eight minutes.
00:48
All right.
00:49
So this is all data that's going to be important to us.
00:52
So step one of doing a significance test is identifying your two hypotheses.
00:58
So first thing we're going to do is we are going to identify what our null hypothesis is.
01:03
Our null hypothesis is that the average wait time is 13 minutes.
01:07
And we need to test for the alternative hypothesis.
01:11
And that is that the mean wait time is less than 13 minutes.
01:15
Okay.
01:16
And we need to do this all at a significance level of 0 .05.
01:20
So once we get our significance values, we are going to see if our p value is less than or greater than that number to reject or to not project our no hypothesis.
01:33
All right, so there's two ways to do this.
01:35
The first thing we need to do is find our t test statistic.
01:42
That's the first thing we need to find.
01:45
You could do that by hand if you'd like.
01:47
And the formula for that is t equals our mean minus our x bar, which is our sample mean, divided by the standard deviation divided by the square root of our sample size...