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April 13, 2021

How to Calculate a Z-Score

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A Z-score is a numerical measurement that describes a value's relationship to the mean of a group of values. Z-score is measured in terms of standard deviations from the mean. 

  • If a Z-score is 0, it indicates that the data point's score is identical to the mean score. 
  • A Z-score of 1.0 would indicate a value that is one standard deviation from the mean. 
  • Z-scores may be positive or negative, with a positive value indicating the score is above the mean and a negative score indicating it is below the mean. 

The calculation you need is Tableau is: 

( SUM([Profit]) - WINDOW_AVG(SUM([Profit])) ) 
 / 
WINDOW_STDEV(SUM([Profit])) 

Replace the SUM([Profit]) with whichever measure you'd like to use at the aggregation that makes sense in your data. 

Get the data used in the video here - https://data.world/vizwiz/car-sales-mock-data

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