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Please Note: This article is written for users of the following Microsoft Excel versions: 97, 2000, 2002, and 2003. If you are using a later version (Excel 2007 or later), this tip may not work for you. For a version of this tip written specifically for later versions of Excel, click here: AutoFill with Random Numbers.
Excel includes a feature that allows you to automatically fill a range of cells with information you have placed in just a few cells. For instance, you could enter the value 1 in a cell, and then 2 in the cell just beneath it. If you then select the two cells and drag the small black handle at the bottom right corner of the selection, you can fill any number of cells with incrementing numbers. This AutoFill feature sure beats having to type in all the values!
You may wonder if there is a similar way to use the AutoFill feature to place random numbers in a range. Unfortunately, the AutoFill feature was never meant for random numbers. Why? Because AutoFill uses predictive calculations to determine what to enter into a range of cells. For example, if you entered 1 into one cell and 5 into the next, highlighted the cells and then used AutoFill, the next number entered in the cell below would be 9 because Excel can deduce that the increment is 4. It is a constant increment that can be predicted.
Random numbers on the other hand are, well, random. By nature they cannot be predicted, else they wouldn't be random. Therefore the predictive nature of AutoFill cannot be applied to random numbers.
However, there are ways around this. One is to simply use the various formulas (using RAND and RANDBETWEEN) that have already been adequately covered in other issues of ExcelTips. These formulas can quickly and easily be copied over a range of cells, using a variety of copying techniques.
Another approach is to use a feature of the Analysis ToolPak which makes putting random numbers into a range of cells pretty easy. Just follow these steps:
Figure 1. The Data Analysis dialog box.
Figure 2. The Random Number Generation dialog box.
ExcelTips is your source for cost-effective Microsoft Excel training. This tip (2964) applies to Microsoft Excel 97, 2000, 2002, and 2003. You can find a version of this tip for the ribbon interface of Excel (Excel 2007 and later) here: AutoFill with Random Numbers.
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