#### The WINDOW_STDEV() function in Tableau is a table calculation function that calculates the sample standard deviation of a given field or expression over a specified window or range of values. It measures the dispersion or spread of data points around their mean within the window.

The syntax for the WINDOW_STDEV() function in Tableau is as follows:

#### WINDOW_STDEV(expression, [start, end])

- expression: The field or calculation for which you want to calculate the standard deviation.
- start (optional): The starting point of the window. If not specified, the window starts from the first data point.
- end (optional): The ending point of the window. If not specified, the window ends at the current data point.

Here's an example to demonstrate how to use the WINDOW_STDEV() function in Tableau:

Suppose you have a dataset that contains information about the monthly sales of different products. You want to calculate the sample standard deviation of the sales values over a rolling three-month window.

- Open Tableau and connect to your dataset.
- Create a view that includes the "Date" field and the "Sales" field.
- Right-click on the "Sales" field and select "Add Table Calculation."
- In the calculation dialog box, choose "STDEV" from the list of table calculation functions.
- Specify the expression as the field or calculation for which you want to calculate the standard deviation (in this case, "Sales").
- Configure the specific settings for the WINDOW_STDEV function, such as the addressing and partitioning options, to define the three-month rolling window.
- Click "OK" to apply the WINDOW_STDEV function to the sales values.

**Tableau will calculate the sample standard deviation of the sales values over the specified rolling three-month window. The standard deviation measures the dispersion of values around the mean, indicating the variability or spread of the sales values within the window.**

You can further customize the view, apply sorting, or add additional calculations based on the calculated standard deviation. For example, you can create a visualization that shows the trend of the standard deviation over time or compare the standard deviations across different products.

The WINDOW_STDEV function allows you to perform calculations related to the sample standard deviation within a specified window. It helps you understand the variability and dispersion of values within a dataset and supports data analysis and visualization based on these measures.

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