Turn on suggestions

Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.

Showing results for

- Home
- /
- Analytics
- /
- Stat Procs
- /
- Wilcox Signed Rank Test Statistic W (not S)

Options

- RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Mute
- Printer Friendly Page

🔒 This topic is **solved** and **locked**.
Need further help from the community? Please
sign in and ask a **new** question.

- Mark as New
- Bookmark
- Subscribe
- Mute
- RSS Feed
- Permalink
- Report Inappropriate Content

Posted 05-22-2018 03:21 PM
(3369 views)

I'm doing non-parametric tests on paired (pre/post) samples that are ordinal (7-point Likert) and non-normally distributed, therefore using PROC UNIVARIATE with the difference of Time1 and Time2.

I know that the test statistic in the SAS output (Singed Ranked, S) is the Wilcox Signed Rank test with its corresponding P value. But it seems like, for the sake of reporting in a manuscript, the literature uses "W" which doesn't seem to be the same test statistic. Do you know how to get this W or do you think I should report the S? (S=-387.5, p<.0001).

Thanks!

1 ACCEPTED SOLUTION

Accepted Solutions

- Mark as New
- Bookmark
- Subscribe
- Mute
- RSS Feed
- Permalink
- Report Inappropriate Content

I think PROC UNIVARIATE is the correct procedure to use here, since you have matched-pairs data rather than two independent samples. The only concern I'd have is that your variables are not continuous but only ordinally scaled. It appears, however, that "many researchers *do* treat Likert scale response data as if it were interval data" (quote from http://pages.cpsc.ucalgary.ca/~saul/wiki/uploads/CPSC681/topic-dane-likert.doc, p. 2, including italics; please see also the caveat described there!).

So, strictly speaking, the *sign test* would be more appropriate -- but less powerful than the Wilcox** on** signed-rank test. Both tests are computed by PROC UNIVARIATE (based on the differences of the paired values), as you can see in your SAS output.

If you go for the Wilcoxon signed-rank test (in spite of the concern), the test statistic S provided by PROC UNIVARIATE differs in fact from the more common test statistic, which is denoted by T^{+} in several standard textbooks on nonparametric statistics. But also the notation *W _{n}*

I think you can report either test statistic as long as it is clear which one you mean (and as you don't misspell "Wilcoxon" ;-)).

3 REPLIES 3

- Mark as New
- Bookmark
- Subscribe
- Mute
- RSS Feed
- Permalink
- Report Inappropriate Content

Non parametric tests are in PROC NPAR1WAY

- Mark as New
- Bookmark
- Subscribe
- Mute
- RSS Feed
- Permalink
- Report Inappropriate Content

Can you explain why I can't use PROC UNIVARIATE? I'm not sure how I would go about using PROC NPAR1WAY since my variables are arranged as such:

(Pre) (Post)

ID Knowledge1_i Knowledge1_ii

1 3 4

2 4 5

3 5 4

...etc

Would I need to recode these variables? Many things I've read say to just take the difference between these two knowledge variables and use PROC UNIVARIATE. Its just I'm not really sure what "S" is. Clear?

- Mark as New
- Bookmark
- Subscribe
- Mute
- RSS Feed
- Permalink
- Report Inappropriate Content

I think PROC UNIVARIATE is the correct procedure to use here, since you have matched-pairs data rather than two independent samples. The only concern I'd have is that your variables are not continuous but only ordinally scaled. It appears, however, that "many researchers *do* treat Likert scale response data as if it were interval data" (quote from http://pages.cpsc.ucalgary.ca/~saul/wiki/uploads/CPSC681/topic-dane-likert.doc, p. 2, including italics; please see also the caveat described there!).

So, strictly speaking, the *sign test* would be more appropriate -- but less powerful than the Wilcox** on** signed-rank test. Both tests are computed by PROC UNIVARIATE (based on the differences of the paired values), as you can see in your SAS output.

If you go for the Wilcoxon signed-rank test (in spite of the concern), the test statistic S provided by PROC UNIVARIATE differs in fact from the more common test statistic, which is denoted by T^{+} in several standard textbooks on nonparametric statistics. But also the notation *W _{n}*

I think you can report either test statistic as long as it is clear which one you mean (and as you don't misspell "Wilcoxon" ;-)).

Build your skills. Make connections. Enjoy creative freedom. Maybe change the world. **Registration is now open through August 30th**. Visit the SAS Hackathon homepage.

What is ANOVA?

ANOVA, or Analysis Of Variance, is used to compare the averages or means of two or more populations to better understand how they differ. Watch this tutorial for more.

Find more tutorials on the SAS Users YouTube channel.