00:01
Let me take notes what's given here, the sample size which is n, this is 380, and the proportion given here which is 0 .25, and the confidence level which was given as 95%, which can be written as 0 .95.
00:16
So we have to find the confidence interval for the proportion.
00:20
So for the proportion, the confidence interval which is the p, this is plus or minus the z alpha over 2, n times the square root of, this is p times 1 minus p, and divided by the sample size.
00:33
This is the formula.
00:34
Let's start solving this question by getting the alpha value which is 1 minus confidence level.
00:39
So the alpha over 2 means this is 1 minus 0 .95 and divided by 2 which becomes 0 .025.
00:46
To get the z alpha over 2, i'm going to use the graphing display calculator application, the inverse norm, and the area from left to right which is 0 .025.
00:56
So the mean of this distribution and the standard deviation which is 1 here.
00:59
To get the inverse norm, just press 2nd and variance the inverse norm here...