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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: Weighted Averages in a PivotTable.
A good example of how to use calculated fields is for summarizing data differently than you can normally summarize it with a PivotTable. When you create a PivotTable, you can use several different functions to summarize the data that is displayed. For instance, you can create an average of data in a particular field. What if you want to create a weighted average, however? Excel doesn't provide a function that automatically allows you to do this.
When you have special needs for summations—like weighted averages—the easiest way to achieve your goal is to add an additional column in the source data as an intermediate calculation, and then add a calculated field to the actual PivotTable.
For example, you could add a "WeightedValue" column to your source data. The formula in the column should multiply the weight times the value to be weighted. This means that if your weight is in column C and your value to be weighted is in column D, your formula in the WeightedValue column would simply be like =C2*D2. This formula will be copied down the entire column for all the rows of the data.
You are now ready to create your PivotTable, which you should do as normal with one exception: you need to create a Calculated Field. Follow these steps:
Figure 1. The Insert Calculated Field dialog box.
Your calculated field is now inserted, and you can use the regular summation functions to display a sum of the calculated field; this is your weighted average.
Since there are many different ways that weighted averages can be calculated, it should go without saying that you can modify the formulas and steps presented here to reflect exactly what you need done with your data.
ExcelTips is your source for cost-effective Microsoft Excel training. This tip (2900) 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: Weighted Averages in a PivotTable.
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