 Hi, this is Dr. Don. I have a problem out of a clay chapter 6, section 0.4, about confidence intervals for a proportion. In this problem, we're given that we had a survey of a thousand homes and found that 100 had overestimated market values. You want to estimate P, the true proportion of the population, with this information. First of all, find P hat. The point estimate is just the proportion there, and so we take 100 divided by 1,000, and that gets 0.1 for our point estimate. And then the correct description of the sampling distribution of P, it's approximately normal because we've gotten an N of 1,000. And if it's more than 30, then that means we can approximate the distribution with a normal distribution. We're going to use the Z formula for getting the confidence interval, but we're going to do it using stat crunch. So the first thing we want to do is click over here on question help, and then open up stat crunch. Okay, I have stat crunch open, and I move things around a bit. All we need to do is go to stat, look down for proportion statistics. This is one sample, and we have summary, since we have the number of successes, which is 100, and the N, the count, was 1,000. We go down here and click on confidence interval for the proportion P, and we want a 90%. So I'm going to change that to 0.90. And I just want to show you, you can click down here to either store your data in a table. I'm going to get the regular output there, but I'm going to get the confidence interval plot as well. And then click compute. And we get our results, and you need to expand the box to see them all. But you can see that our lower limit is 0.084, and our upper limit is 0.115. So they want two decimal places in their particular. So 0.084 rounds to 0.08, and 0.115 rounds to 0.12, which is the answer they have there. The next thing is to interpret the confidence interval, and that is the same. We can be 90% confident the interval contains a true value of the proportion P, the population proportion. And then we want to test a claim. Is the claim that P equal 0.05 believable? We can do that a couple of ways. Later on in the course, we will do hypothesis tests like this. And that's where we are will actually be comparing the standard deviations, if you will, the Z scores to see if it's greater than our alpha level. But here we just need to check, is this value inside the confidence interval? And it's not. It's not inside the confidence interval. Therefore, it is not a reasonable estimate or reasonable claim. And over here, if we look at our stat crunch, and we click the little error, we get a confidence interval drawn, and you can see it goes from roughly 0.085 to 0.115. But of course, 0.05 is way over here. So it's definitely not in that confidence interval. So that's how fast you can do a problem like this using stat crunch. I'll show you how to do this using Excel in another video.