0 Replies Latest reply on Aug 14, 2014 8:38 AM by Laetitia Tlemsani

# Significance test for porportion

Hello there,

I wish to submit a problematic encounter with Tableau on a calculation of significance. I work with a file of survey results as follows:

 Year Category_1 Weighted_responses Nb_surveys 2013 A 5,057,576 15,030 2013 B 9,888,532 36,375 2013 Etc. … … 2012 A 5,477,234 15,444 2012 B 10,512,112 36,529 2012 Etc. … …

I want to know for each case (A, B, etc.) in each category, if the proportion in 2013 is significantly different from the one in 2012, and I only want to show the difference in point between these two proportions if this difference is indeed significant.

Usually I make it in Excel with a significance test which is calculated as follows:
Test=(P1 – P2)/sqrt(P(1-P)*(1/N1+1/N2)).

With the figures in the table above, we have for the case A:
• P1 = 5,057,576 / (5,057,576 + 9,888,532 + ...)
• P2 = 5,477,234 / (5,477,234 + 10,512,112 + ...)
• P = (5,057,576 + 5,477,234) / ((5,057,576 + 9,888,532 + ...) + (5,477,234 + 10,512,112 + ...))
• N1 = 15,030
• N2 = 15.444

I have to do the exercise on categories that may have more than 50 cases, so I have to use a dynamic formula.

I don't know how to figure it out in Tableau. Could you help me on this ?

Thanks a lot !

(by the way I'm french, sorry for my english ! )