You would need to create a calculation just like any other. It would involve window calculations as you would need to know what was to be trimmed. Do you have a formula you would like to use?

Take a look at this.  I think this is correct, but please check the calculation.

Realized a lower parameter control would be useful as well   Updated.

Hi Ben,

Thanks for posting this one. In the calculated field "Percentile", what is the purpose of subtracting .05 from INDEX()?

Percentile

(INDEX() -.05)/Total(Count([OrderID]))

--Tim

Tim,

Great question, maybe you can help answer it.  I was using reference material from Stanford

http://www.stanford.edu/class/archive/anthsci/anthsci192/anthsci192.1064/handouts/calculating%20percentiles.pdf

Wikepedia has same equation.

http://en.wikipedia.org/wiki/Percentile

I sold my stats textbooks many many many moons ago.  Can anyone help answer?

Hi Ey,

The reason that it's not calculating correctly is that you don't have a unique id for the sale; I added a concatenated field Month + Outlet and it calculated properly.  Also the trimmed mean you have on the monthly view is not calculating properly, it should go down when you lower the upper threshold (eliminating high range from median calculation).  Why it's doing that is beyond me right now.

Hi Ben,

Thanks for posting a link to those papers. I see the calc in the Stanford paper and will dig deeper this weekend. It will give me a little light reading for the weekend.

--Tim

A few years later, here's a version of TRIMMEAN() in Tableau that uses Level of Detail expressions:

TRIMMEAN() in Tableau | Drawing with Numbers

Jonathan