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Feb 13, 2020 1:42 PM
(692 views)

I am attempting to complete a non-parametric test on skewed data that is non-symmetric. I am using the test means option in the distribution window but the Wilcoxon Signed test requires symmetry and this skewed data is non-symmetric. Is there an option to so a 1-sample sign test instead of the Wilcoxon test?

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Created:
Feb 13, 2020 2:09 PM
| Last Modified: Feb 13, 2020 2:11 PM
(688 views)
| Posted in reply to message from pickerins 02-13-2020

It is fairly easy to create the sign test.

Create a new column that is a conditional formula. Specify the value 1 if the original data is greater than your target, 0 otherwise (note that I am assuming there are no values equal to the target. If that occurs, most texts recommend removing that observation from the data).

This formula column should have a Nominal modeling type. Now make a distribution of that column. From the red popup, choose Test Probabilities. Typically the hypothesized probabilities are 0.5. You will have two different tests. The Likelihood Ratio test will match most of the "by hand" calculations that are mentioned in text books. Typically, both tests will agree on the conclusion.

Dan Obermiller

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Created:
Feb 13, 2020 2:09 PM
| Last Modified: Feb 13, 2020 2:11 PM
(689 views)
| Posted in reply to message from pickerins 02-13-2020

It is fairly easy to create the sign test.

Create a new column that is a conditional formula. Specify the value 1 if the original data is greater than your target, 0 otherwise (note that I am assuming there are no values equal to the target. If that occurs, most texts recommend removing that observation from the data).

This formula column should have a Nominal modeling type. Now make a distribution of that column. From the red popup, choose Test Probabilities. Typically the hypothesized probabilities are 0.5. You will have two different tests. The Likelihood Ratio test will match most of the "by hand" calculations that are mentioned in text books. Typically, both tests will agree on the conclusion.

Dan Obermiller

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Re: Non-Symmetric 1-sample median test

Thank you for this!

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