00:02
Our goal here is to create a 90 % confidence interval for the mean iq score of students at this particular college.
00:10
So to do that, we're going to be using this formula, x bar plus or minus t star times s over the square root of n.
00:16
And as we go to calculate this confidence interval, we'll answer some of your other questions along the way.
00:22
So question a, what is the point estimate? that is our x bar, our sample mean, which is 105 .2.
00:30
So there's the answer to question a.
00:33
Sample mean point estimate 105 .2.
00:37
Now it says next, find the critical value, which is going to be our t star in this formula.
00:44
So for that, we're going to need the t distribution table, probably found in the back of your textbook.
00:50
And we're going to be using a degrees of freedom of 74, sample size minus 1.
00:58
But there is no 74.
00:59
So we're going to go down to degrees of freedom, 60, at 90 % confidence.
01:06
So as we go across that table, we cross row 60, down 90 % confidence.
01:11
T -star is 1 .671...