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# Why Error Checking is Important

3:04 with Tyler TallonNow let's learn about the importance of error checking and look at some effective ways to check your work.

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Please note that **this is a new spreadsheet**, different from the one you used in the previous stage:

[MUSIC] 0:00 So far in this course we've learned how to use look up functions, 0:09 create a pivot table, and learned how to use several other tools in Excel. 0:13 Now we're going to learn about the importance of error checking, 0:17 which has saved me so many times. 0:20 And I'm excited to show you some effective ways to check your work. 0:22 Before we dive in to the error checking process, 0:26 let's first discuss some common errors in Excel. 0:29 Generally, there are four different types of errors. 0:32 Input errors, which are data entry errors or missed data. 0:35 Output errors, usually caused by incorrect cell referencing, problems with time or 0:39 date switches or graphic outputs not updating properly. 0:44 Conceptual logic or using the wrong formula. 0:48 And then formula errors, which could be using the correct formula but 0:51 typing it incorrectly, or the wrong order, or 0:55 incorrect parenthesis, basically just bad math. 0:58 Let's drill down a little further on some of these errors by looking at 1:01 a few examples on our spreadsheet. 1:04 First, let's look at a common error that can come from adding rows. 1:07 Here we have store sales by state in month for the first half of the year. 1:12 Let's say we want to say a sum to get the total at the bottom. 1:16 Let's sum each month by using the AutoSum feature up at the top right. 1:19 And then let's copy this over for each month. 1:24 Okay, now let's add a row to our data. 1:28 For newer worksheet versions like I'm using, if you add 1:35 a row in the middle of your data, then the sum range will automatically update. 1:39 You can see this by double clicking on the sum row, and 1:44 a box will appear around the group of cells that it's summing. 1:47 It's always good to double check this when you add rows. 1:51 But now let's try adding a row at the top. 1:54 If I add a row here, And then double-click on this sum row, 1:57 you'll notice that the top row is not included in my sum. 2:03 So if I were adding data for Alabama here, 2:07 You'll see it's not included in the sum. 2:26 To correct this, you can just change the formula to start at B2 instead of B3. 2:30 Now you can see it's including every state. 2:45 And then you'll want to make sure to copy that formula over to the remaining months. 2:48 Now just to make sure it copied correctly, let's double-click on June's total. 2:52 Yep, looks like I copied over correctly. 2:57 Coming up, we'll keep looking at some common errors and 3:00 learn about how to avoid them. 3:02

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