 I hope you find this video helpful. And if you do find it helpful, please subscribe to my YouTube channel, TheStatsFiles. Click the big red subscribe button. Hi, this is Dr. Don. I have a problem out of Chapter 8 and it has to do with a confidence interval for a difference in proportions. We read it and we're told that we have a survey of a million 68,000 students and that 9.8% were planning on studying engineering. Another survey of 1.476 million students, 9.2% said they were going to study engineering and they want a 90% confidence interval for the difference between proportions P1 minus P2. And we're assumed that the samples are random and independent. Now we're given this big equation here. And you can use that to find the confidence intervals, but it's a lot quicker using StatCrunch. So let's go over to StatCrunch. You can go to StatCrunch by clicking on question help and opening StatCrunch that way. Okay, we're in StatCrunch. We go to Stat, proportion stats, two samples with summary because we have summary data. We need the number of successes, but we're given percentages. And you can get around it by just typing in an equation, 0.098 for 9.8% times 1,068,000 and the observations 1068,123. The number of successes of sample 2 was 0.092% times 1,476,000, put the 1,476,000 again and I'll double check that. We want the confidence interval and we want a 90%, so I'll change that to 0.9 and click compute. We get our answer. We've got our first count and the total, second count, the total, the point estimate, the sample difference 0.006 and over here we've got our lower limit and that rounds to 0.005 and our upper limit rounds to 0.007. And I'm pretty sure those are the answers they wanted, 0.005 and 0.007. So I hope this helps. And if it does help, please consider subscribing to my YouTube channel, TheStatsFiles. Just click the big red subscribe button.