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1. Re: T-Test calculation
best to provide details on the calculation you want to perform.
From looking at http://www.socialresearchmethods.net/kb/stat_t.php I am not sure how the t-test concept described there fits with your description.
If you can provide your logic, and sample data, a calculated field can be provided.
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2. Re: T-Test calculation
I also found http://www.jerrydallal.com/LHSP/psd.htm and with both those references, I was able to make the attached.
Is this what you are looking for?
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3. Re: T-Test calculation
Joe,
I had a feeling either you or Andy would pipe in on this quickly.
A colleague gave me a simple spreadsheet that shows how in Excel to compute the T-Test. To be honest, I'm not sure if it is correct but if it is then your approach needs a couple of modifications.
Have a look at the attachment (cells A1 and B1 contain the response counts).
Thanks.
Steve
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4. Re: T-Test calculation
after a little bit of searching, I think what you are looking for is called the two-proportion z-test (at least the Excel formula used matches the results).
I did the calculation two ways in the workbook, one calc field for each concept, and another as a single calc.
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5. Re: T-Test calculation
Joe,
I forgot to mention how much I like the sum(1) trick. I had been using countd(ID), but really like the simplicity of sum(1).
This looks right to me, but I need to find out if this is what is wanted or the t-test (this is not my area of expertise, but a great opportunity to learn new stuff.)
Also, you are correct that the values should be negative.
Very cool (and thanks for doing both the single and dual calc versions).
Steve
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6. Re: T-Test calculation
SUM(1) is the same thing as SUM([Number of Records]), it feels like less typing/clicking for me, just a personal preference.
Whereas COUNTD([ID]) is not always the same as SUM(1), but I can imagine situations where they would be the same, it depends on your data and situation.
Here is the reference that I used, they provide some sample situations/questions as well:
http://stattrek.com/AP-Statistics-4/Test-Difference-Proportion.aspx?Tutorial=AP
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7. Re: T-Test calculation
Joe,
Got you on the SUM(1) thing.
Thanks for the link and your generosity.
Steve
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8. Re: T-Test calculation
Hello Joe.
I have a similiar question about T-test for "mean", rather than proportional.
Do you know how to create same calculation in Tableau for the excel function T.Dist.2T(% lift from mean of treatment group vs. mean of control group, degree of freedom)?
Thanks.
Rochelle
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9. Re: T-Test calculation
Rochelle,
Can you please provide a sample Excel file that performs the calculation you are looking for?
Also I recommend starting a new thread
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10. Re: T-Test calculation
Hi Joe.
I attached an excel file with sample calculation in my post above. Basically I need a similiar calculation in Tableau to achieve the T.DIST() function in excel to get p-value of a T-test.
I will start a new thread too.
Please let me know if you have any insights. Thanks!
Rochelle