Share your ideas for the JMP Scripting Unsession at Discovery Summit by September 17th. We hope to see you there!
Choose Language Hide Translation Bar
Highlighted
Level I

## Non-Symmetric 1-sample median test

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?

1 ACCEPTED SOLUTION

Accepted Solutions
Highlighted
Staff

## Re: Non-Symmetric 1-sample median test

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
2 REPLIES 2
Highlighted
Staff

## Re: Non-Symmetric 1-sample median test

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
Highlighted
Level I

## Re: Non-Symmetric 1-sample median test

Thank you for this!
Article Labels

There are no labels assigned to this post.