![]() ![]() You can edit the field as a table calculation. When you use a calculated field that includes a table calculation function in a view, it's the same as adding a table calculation to a field manually. The Z-Score function, in turn, is a table calculation function because it includes STDEVP Sales in its definition. The STDEVP Sales function is based on the WINDOW_STDEVP function, which is a table calculation function. Notice that the Z-score field on Columns has a table calculation icon on the right side (that is, a small triangle): ![]() ![]() (SUM() - ) / ĭrag Z-Score from the Data pane to Columns and State to Rows. Name the calculation Z-score and type or paste the following in the formula area: Name the calculation STDEVP Sales and type or paste the following in the formula area:Ĭreate one more calculated field, this one to calculate the z-score. Name the calculation Average Sales and type or paste the following in the formula area:Ĭreate another calculated field to calculate the standard deviation. ![]() This article demonstrates how to calculate a z-score in Tableau.Ĭonnect to the Sample - Superstore data source provided with Tableau Desktop.Ĭreate a calculated field to calculate average sales.Ĭhoose Analysis > Create Calculated Field to open the calculation editor. That is, they are statistically significant outliers. What is the relative score of one distribution versus another? For example, Michael is taller than the average male and Emily is taller than the average female, but who is relatively taller within their gender?Īs a general rule, z-scores lower than -1.96 or higher than 1.96 are considered unusual and interesting. What values can be considered exceptional? For example, in an IQ test, what scores represent the top five percent? What percentage of values fall below a specific value? In cases where it is impossible to measure every observation of a population, you can estimate the standard deviation using a random sample.Ĭreate a z-score visualization to answer questions like the following: To calculate a z-score you must know the population mean and the population standard deviation. In statistics, the z-score (or standard score) of an observation is the number of standard deviations that it is above or below the population mean. ![]()
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