1 00:00:00,000 --> 00:00:02,500 2 00:00:02,500 --> 00:00:08,500 Hello, and welcome to a video on summation in Excel. Summation is when simply 3 00:00:08,500 --> 00:00:14,566 put, we want to find the sum of something. So either a sum after a set of calculations or the 4 00:00:14,566 --> 00:00:14,599 5 00:00:14,600 --> 00:00:20,833 sum of a data point, meaning a set of numbers, that sort of thing. 6 00:00:20,833 --> 00:00:20,999 7 00:00:21,000 --> 00:00:27,300 So let's say we have a problem that's asking us to find the sum of x. Well, 8 00:00:27,300 --> 00:00:33,333 here's x right here. We can see that it's this collection of data. To find the sum in Excel, 9 00:00:33,333 --> 00:00:39,399 we type equals sum, open parentheses, select 10 00:00:39,400 --> 00:00:39,566 11 00:00:39,566 --> 00:00:45,299 the variable that we'd like to find the sum for, close parentheses and hit enter. 12 00:00:45,300 --> 00:00:45,766 13 00:00:45,766 --> 00:00:51,899 And we can see that the sum of x is 44. And if you calculate this by hand, you can see that 14 00:00:51,900 --> 00:00:51,933 15 00:00:51,933 --> 00:00:57,999 that's the case. We can also find x bar 16 00:00:58,000 --> 00:00:58,366 17 00:00:58,366 --> 00:01:04,732 in Excel. x bar is the average of a sample. So in Excel, we'll 18 00:01:04,733 --> 00:01:09,633 type equals average, open parentheses, 19 00:01:09,633 --> 00:01:11,099 20 00:01:11,100 --> 00:01:17,166 select the variable we'd like to find the average of, close parentheses and hit enter. 21 00:01:17,166 --> 00:01:17,632 22 00:01:17,633 --> 00:01:23,866 And you can see now, we have the average or x bar. We can do other 23 00:01:23,866 --> 00:01:29,932 types of calculations in Excel as well. If we wanted to multiply x times y, we could do that 24 00:01:29,933 --> 00:01:36,633 by saying equals x, asterisk, then selecting 25 00:01:36,633 --> 00:01:36,799 26 00:01:36,800 --> 00:01:42,866 y, and hitting the enter key. To repeat this 27 00:01:42,866 --> 00:01:47,032 down the line, we'll just drag it from the corner here. 28 00:01:47,033 --> 00:01:50,199 29 00:01:50,200 --> 00:01:56,033 If I then wanted to find the sum of these numbers, I would type equals sum, 30 00:01:56,033 --> 00:01:57,466 31 00:01:57,466 --> 00:02:01,566 select the numbers, and close parentheses. The same is before. 32 00:02:01,566 --> 00:02:03,899 33 00:02:03,900 --> 00:02:10,200 Let's try x minus y. So open an equation by using the equals 34 00:02:10,200 --> 00:02:15,400 sign, then select a2 minus b2 and hit enter. 35 00:02:15,400 --> 00:02:19,800 36 00:02:19,800 --> 00:02:25,933 And that's it. That's all you have to do to find the difference between two variables. Now, if we want to know 37 00:02:25,933 --> 00:02:25,966 38 00:02:25,966 --> 00:02:30,532 deviation or deviants, what we're looking for is x minus x bar. 39 00:02:30,533 --> 00:02:32,799 40 00:02:32,800 --> 00:02:39,133 So we would say equals x minus and x bar down here is this 41 00:02:39,133 --> 00:02:39,166 42 00:02:39,166 --> 00:02:45,166 number. To make it stay on that number, to make this number a constant. We're going 43 00:02:45,166 --> 00:02:45,199 44 00:02:45,200 --> 00:02:51,266 to use the dollar sign in front of a and the dollar sign in front of 13. This tells Excel when I drag this 45 00:02:51,266 --> 00:02:54,299 formula down, don't move this box. 46 00:02:54,300 --> 00:02:57,900 47 00:02:57,900 --> 00:03:04,233 Okay, now we're going to drag that down. Let's 48 00:03:04,233 --> 00:03:04,266 49 00:03:04,266 --> 00:03:10,732 find the sum of our deviants. Here 50 00:03:10,733 --> 00:03:13,899 51 00:03:13,900 --> 00:03:16,200 we go. 52 00:03:16,200 --> 00:03:22,366 53 00:03:22,366 --> 00:03:27,399 As expected, the sum of our deviants is zero. This will always be the case. 54 00:03:27,400 --> 00:03:28,933 55 00:03:28,933 --> 00:03:34,933 What if we want to define the square of x minus x bar? There are a couple of ways 56 00:03:34,933 --> 00:03:41,133 we could do that. We could say equals e to times e to 57 00:03:41,133 --> 00:03:41,299 58 00:03:41,300 --> 00:03:46,833 just like before when we found x times y except for multiplying it by itself. And that will get 59 00:03:46,833 --> 00:03:47,966 60 00:03:47,966 --> 00:03:52,299 us 4.714 squared and we could drag that down. 61 00:03:52,300 --> 00:03:54,466 62 00:03:54,466 --> 00:03:57,266 We could also use 63 00:03:57,266 --> 00:04:02,999 64 00:04:03,000 --> 00:04:08,166 the power function equals power, 65 00:04:08,166 --> 00:04:09,432 66 00:04:09,433 --> 00:04:15,433 select the number, and then select the power. Which in this case is 67 00:04:15,433 --> 00:04:15,466 68 00:04:15,466 --> 00:04:20,632 2 because we'd like to square it. It enter and then you would drag it down. 69 00:04:20,633 --> 00:04:22,299 70 00:04:22,300 --> 00:04:28,566 There is another way that you can find a square in Excel. And that's 71 00:04:28,566 --> 00:04:28,599 72 00:04:28,600 --> 00:04:34,566 by using the carrots symbol. So equals x minus x bar 73 00:04:34,566 --> 00:04:35,799 74 00:04:35,800 --> 00:04:41,800 raised to the power of 2. And we're using 2 again because we want to 75 00:04:41,800 --> 00:04:41,833 76 00:04:41,833 --> 00:04:48,033 square it. If we wanted to cube it, then we would use 3. If we wanted to raise it to the fourth or fifth power, then we would 77 00:04:48,033 --> 00:04:48,066 78 00:04:48,066 --> 00:04:54,266 use 4 or 5. Okay, so now that we've got x minus x bar squared, what if we wanted to find 79 00:04:54,266 --> 00:04:54,299 80 00:04:54,300 --> 00:05:00,166 the sum of x minus x bar squared? Well, of course, we would calculate that the same way we did before using 81 00:05:00,166 --> 00:05:00,432 82 00:05:00,433 --> 00:05:06,433 the equal sum function. And that's it. That's the sum of x 83 00:05:06,433 --> 00:05:07,899 minus x bar squared.