The divisor in the standard deviation formula is different depending on whether you want the standard deviation for a data set that represents the entire population (divide by the number of data elements minus one), or if your data set is a sample of the population, and you want to calculate the standard deviation to generalize your results to the entire population (divide by the number of data elements). As a result, Excel provides the following four functions to calculate standard deviation based on whether you want to calculate the statistic for a population or a sample, and how you want to treat text and logical values in your data set:

**STDEV.P**- Calculates the standard deviation for a**population**and**ignores**logical and text values.**STDEV.S**- Calculates the standard deviation for a**sample**and**ignores**logical and text values.**STDEVPA**- Calculates the standard deviation for a**population**and**converts**"False" and logical False to zero and "True" and logical True to 1.**STDEVA**- Calculates the standard deviation for a**sample**and**converts**"False" and logical False to zero and "True" and logical True to 1.

## Calculate Mean

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Launch Excel and either open a workbook that has the data for which you want to calculate statistics or type the data into the blank workbook. For an example, consider a workbook with test scores for a population of 10 students that does not include any text or logical data. The workbook also contains an area in columns D and E to display the calculated statistics.

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Click in the cell that will display the mean value for the population and then choose the function selector, ** fx**.

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Change the category selection box to **Statistical**. Scroll through the list of functions, choose **AVERAGE** and then select **OK**.

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Click the cell selector button to choose the cells that contain your data.

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Use your mouse to highlight the range of data cells or type the range into the Function Arguments box, for example, **B2:B11**. Choose **OK** to place the calculation in your workbook.

## Calculate Standard Deviation

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Click the cell that will display the standard deviation and click the function selector, ** fx**.

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Choose the **STDEV.P** formula to calculate the standard deviation for the entire population and to ignore text and logical values. The category selection box defaults to Statistical based on your previous selection. Choose **OK** to continue.

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Click the cell selector button to select the range of values.

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Select the range of data cells or type the range in the Function Arguments box and choose **OK**.

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**Right-click** in the cell that displays the standard deviation and choose **Format Cells...** from the menu.

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Select the number of decimal places you want to display and choose a format for negative numbers.

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Review the results to ensure they look reasonable given the data set.