 Hi, this is Dr. Don. I have a problem out of Chapter 4, Section 7, and this has to do with the normal distribution. It says that if a population data is normally distributed, what is the portion of measurements you would expect to fall within the following intervals? And they give us mu plus sigma plus or minus sigma, mu plus or minus 2 sigma, mu plus or minus 3 sigma. We can do this very quickly using stat crunch. Remember, you just go up to question help and open stat crunch there. I've already got stat crunched open just to save a little bit of time. And what I'm going to do here is just go into stat calculators normal. Now, if you haven't discovered this normal calculator or these other probability distribution calculators, you will find them very, very, very handy and they will stop a lot of dumb mistakes that you will make if you try to go into the tables. Here we're talking about the standard normal distribution with a mean of 0 and a standard deviation of 1. And we want to know plus or minus sigma. That's one standard deviation. So we can click on the between tab here and it comes up default minus 1 plus 1, which is what we want. And that is 0.68%. Remember, probabilities are always between 0 and 1. A few of the problems in my stat lab may ask you for fractions. But in most cases, you need to put in decimals. And it's always from 0 to 1. The second part is plus or minus 2 sigma. And remember, sigma, we convert to the normal distribution is just z, our z score. So we'll put minus 2 plus 2 in our between calculator, hit compute, and we get 0.95, which is the answer there. The third one is plus or minus 3 sigma plus or minus 3 z. So it would be from minus 3 z to plus 3 z. Click compute. And that's 0.997. If you round that to do decimal places, it's 1.00. So that's how fast you can do normal distribution probabilities using this stat crunch normal calculator. I recommend you use it.