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:

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.