00:01
So we have a random sample of 50 for the number of people on a flight, and we want to find a 95 % confidence interval for the mean.
00:12
And when we do that calculation, we find that the mean, i put all that data into a list, and i find that the mean is 136 .22 passengers with a sample standard deviation of 24 .439.
00:28
And we will be using a t value with 49 degrees of freedom, and our alpha level is 0 .05, and we have the degrees of free, excuse me, the upper tail will have 0 .025.
00:49
And then our table, you know, my table only has 50 degrees of freedom.
00:54
It doesn't have 49, and i'm going to figure out what it is in the second.
00:58
But if you used 50, you would get it's approximately 2 .009.
01:03
And i'm actually going to use my software just one second.
01:10
And my software, if i use my inverse t value, and i type in the area of 0 .025.
01:23
And i'm going to actually get a negative value here and then 49 degrees of freedom.
01:27
I'm going to get that that value comes out to be in the upper tail, but be positive.
01:33
And it would come out to be almost this.
01:35
It comes out to be 2 .0096.
01:39
So it could use 2 .010 if you're using a three -place decimal...