 Here's our video tutorial for using Microsoft Excel to compute some descriptives of interest. We're going to start with the median. The median is the middle value. It means half of the- You see, we already did some in average last time. Yes. That's what you're looking at. Now, we're going to show how to do a median. What is the median? The middle value, the 50th percentile. Half the data is above it and half is below it. If you get a median score in a class, you know that you beat half the class, but half the class beat you. You're on the line. Right in the middle, the median. We're going to do median now. Watch. First, I type median, middle value, okay. Now, I go to the function wizard. I look for median. Let me find it. There's median. Oops, I lost it. There's median. I say, okay. Again, you got to make sure you got the data set. The data set, as you know, is D2 to D13. D2 to D13. Okay, that's called my input data. So we type in D2. Maybe we can just grab it. You can do it that way. It went too high. It went too far. There we go. Maybe we'll do that. Did that work? We grabbed it, yes. And it's D2 to D13. Yes. Great. Let's click okay. Right, and there we go. There's the median. 71.5. That means half the class, if this is a class of 12 students, half did above 71.5, half are below it. Okay, and generally, these kind of statistics, you may not want to use for 12 observations, especially the next one called quartiles. Now, when you talk about a quartile, that's the first quartile is essentially the 25th percentile. It means 25% are below you, 75% are above you. So you don't write quartile. You have to indicate which one. So I'm going to type Q1, first quartile. While you do that, I'll just explain. You have your three quartiles that break up your data set into four equal pieces. You're taking a data set and making three cuts in order to make it, turn it into four equal pieces. Q1 is the first quartile. 25% of the data is smaller than that value, 75% greater, and so on. Okay, so you did Q1, Q3. We already know Q2. Q2 is the same as the median, which is also the same as the 50th percentile. Exactly. So let's get Q1. Go to the function wizard, look for quartile. Now, this exclude include, don't worry about that. Because if you have no missing data, it's the same either way. Some days you have an issue, we have a huge data set, let's say 200 values, and let's say two of the values could be words, like yes or no or something. So the question is whether you want to exclude them, because it affects the sample size. So don't worry about it, because we don't have that in this course. For this course, I wouldn't worry about it. Yeah, so I'm going to use the first one, exclude. There's nothing to exclude. Okay, I say okay. And now notice, now it's calling it an array. What a cold number before is now an array. So I'll let you grab the data. Grab it again. Grab the data, from D2 to D, D13. Data's been grabbed. There we go. Okay, there it is. And now, quart. You want to know which quartile you're asking for. So it tells you, if you look at the bottom, quart is a number. Well, minimum value is zero. Zero doesn't make no sense. That's just to get the minimum. It's not really a quart. You don't need it. Yeah, you don't need to call that a quartile. Yeah, they're really just Q1 and Q3. The median is Q2. So let's do right one. I want the first quartile here. And now I say okay. Now that's the quartile. Again, with a data set of 12, it's kind of ridiculous to break it up into quartiles and we're going to do percentiles soon. But you get the idea. In the real world, you might be working with five million numbers. You can do that one on your own. I'm not doing that for you. No, let's do it. Let the class type in five million numbers. They have nothing else to do this weekend. Okay, now we did Q1. You can just copy the formula from Q1 into Q3 and change the one into a three. That's too advanced? Too advanced. Okay. We always do things easy. Here's Q3. You look for quartile again. Okay. And now I'll let you grab the data. We know where the data is located. D2, all the way down to D13. And now it says quart. You put in a, it's asking for a number like zero, one, two. You don't want zero. The three, that's the third quartile. And this is the value for which 75% of the data is smaller, 25% of the data is larger. Now the next thing we're going to do is percentile. Now there are 99 actual percentiles. We're cutting up the data into 100 equal sized pieces. Okay. So P1 would be the first percentile. P2 is the second percentile. As a matter of fact, P25, the 25th percentile, that means you're above 25%, but 75% are above you. That's the Q1. The 50th percentile is also the median. The 75th percentile is the third quartile. So when you say percentile here, you have to indicate which one. So we're going to make this just randomly, the 80th percentile. Oh, okay. I was going to ask for the 90th. Because if these are exam scores and you're in the 90th percentile, you want to go home and tell your parents that. All right, so we'll ask for that. Again, with 12 observations, you don't really calculate 90th percentiles. Okay, I'm going to let you enlarge this. Nobody knows who's doing it. Yeah, but we have to make it bigger. Notice how we widened the column. Good idea to widen the column. You see, you do it, you go all the way up. When you see that black cross. Highlight the column. And I can make it bigger, smaller, drag it. I made it a little too big, but all right. Good enough. All right, but plenty of room to work. So now, again, I'm going to use the 90th percentile. It could have been, really, if you have nothing to do this week, you'll put in a hundred numbers and get the first percentile P1, second percentile P2, third percentile P3, then P4. Make sure to enter millions of numbers first. Go right ahead. Yes, okay. We're doing the 90th percentile. Okay, so now I go to the function wizard. I look for percentile. Again, with the exclude, don't worry about that. You have the same with the exclude, include. Okay, but you want percentile? Okay, we'll take the exclude. Now don't, it's not percent rank, it's percentile. And the exclude is, don't worry about that. You want percentile? I say, okay. Okay, now here's the array. We know that's D2 to D13. I'm going to let my colleague... Let's put in the array. My colleague is going to... I have a very important job here. Yes, you put in the array correctly. Now K, it's, we want the 90th percentile. Now, some growers, you might put the number 90, but they're asking for a value between zero and one. So you have to put 0.90. For 90th percentile, it's 0.90. Suppose we want to the 77th percentile. You'd be putting in 0.77. Okay, so make sure it's a decimal between zero and one as per instructions. So 0.90 gives you the 90th percentile. And I say, okay. And there I got the 90th percentile. 99, again, with 12 numbers, this is a kind of little ridiculous. But you get the idea. That I'm showing you how to get the percentile. The last thing... One more thing. We already saw how to get the mean. The complement to that is the standard deviation if you want a lot of quantitative information, you're usually getting a mean and a standard deviation, right? Yeah, standard deviation is something you've heard. You learn about it. It's a measure of dispersion. And you should know how to get it. Okay, watch how easy it is. Now you have to be careful. There's actually two kinds of standard deviations. If you're working with a sample, you'll find that in the formula, you divide by n minus one. But losing a degree of freedom. If you're working with a census, then you use standard deviation for a population and you divide by n, the sample size. You'll learn more about that in your course. We're just pointing it out now. So you know what formula to use. Yeah, this way you can impress your boss because you're gonna be confused otherwise. You see the standard deviation, stdev.p. p stands for population or parameter. It's when you have a census. And this cause in most places, you're gonna be working with a sample. You've taken a sample. So you need standard deviation.s for sample or a statistic. Okay? And I'll say, okay. And again, now it's calling it not an array. We're back to using the number. So the d2 to d13. And now, that's all you need. You just added a number. You didn't need that. It wasn't necessary. But that's all you need. So we have the data's located and I say, okay. And there's your standard deviation. Okay, so now we've learned how to get a standard deviation. And there are other statistics. We may wanna change the number of significant digits here. Format cells make it a number with just two significant digits. And that just looks a little nicer. Depending, you ask your teacher what you should do with that. You can also add this in the menu. There's a place to add decimals. You'll see the menu is a place where it says you can add decimals or subtract decimals. That's another way to do it. But most of the time, two decimal places are more than enough. So now we've learned how to get various descriptive statistics. And good luck. All right, do your homework.