Reusable Z-Test for 1 or 2 Independent Means

Version 5

    Description:

     

    There has been a lot of discussion on the forums about getting basic statistical tests into Tableau.  With the assistance of a couple of other members, I was able to create a completely reusable Z-Test which I have found to be faster than using R.  I have an in-depth blog post about using this file (with pictures!) at http://breaking-bi.blogspot.com/2013/04/conducting-1-and-2-sample-z-tests-in.html.

     

    Prerequisites:

     

    Data set stored in Excel.

    Does not have to be at the appropriate grain.

    The workbook will handle any and all necessary aggregations.

     

    Directions:

     

    Open the attached .twbx

    Right-Click the Excel Data Source

    Edit Connection (Change to your Excel Worksheet)

    Edit the following calculated fields:

         Value: The measure you would like to use in your test, along with the aggregation function to be used, such as SUM() or MAX()

         Grain: The dimension of the grain you would like your measure aggregated to.
         Slicer: The dimension you would like to use to create your two samples.

    Use the quick filter on the right side to select which slices you would like to use.

         Selecting 1 slice will compute a 1-sample Z test against the Theoretical Mean Parameter

         Selecting 2 slices will compute a 2-sample Z test.

     

    That's it.  Your Z-Test has been completed.  Now, you can slice your data any way you would like and can look for any patterns.  I've found that this quite a bit faster than using R to pull in your data, separate it into 2 data sets, then perform the test.

     

    5/22/2013:

     

    There is now a 2nd worksheet that allows you to compare the histograms for the two sets of data.  This was not simple and there is a blog post explaining the technique at http://breaking-bi.blogspot.com/2013/05/creating-histograms-in-tableau.html.

     

    Example Calculation:

     

    Capture.PNG


    Comments:

     

    The P-Value formula came from

     

    http://web2.uwindsor.ca/math/hlynka/zogheibhlynka.pdf

     

    Related Calculations:


    Reusable Simple Linear Regression:

     

    http://community.tableau.com/docs/DOC-1479

     

    Revision History:

     

    4/26/2013: Added in-depth blog post for use.

    5/22/2013: Added histograms

    7/3/2013: Added "Related Calculations" Section

                    Updated the workbook to include histogram labels.