turn on suggestions

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

Showing results for

- JMP User Community
- :
- Discussions
- :
- Discussions
- :
- Wilcoxon vs Steel Dwass

Topic Options

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

- Mark as New
- Bookmark
- Subscribe
- Subscribe to RSS Feed
- Get Direct Link
- Email to a Friend
- Report Inappropriate Content

Jan 10, 2016 3:14 PM
(5592 views)

Hi,

I am wondering which test in JMP to run for my data. I am comparing different groups of birds and have different sample sizes for the groups. My understanding is that the Wilcoxon test compares medians and Steel Dwass compares means? In creating graphs, would I use the mean and standard error or medians and confidence intervals?

Thanks!

1 ACCEPTED SOLUTION

Accepted Solutions

- Mark as New
- Bookmark
- Subscribe
- Subscribe to RSS Feed
- Get Direct Link
- Email to a Friend
- Report Inappropriate Content

These are both non-parametric tests so I think they will both work with rank calculations and hence are comparing medians not means. The distinction between the two is that the Wilcoxin test performs pairwise comparisons (it is the non-parametric equivalent of performing a Student's t test on each pair); the alpha level is fixed and takes no account of the number of comparisons being performed. The Steel Dwaas method performs the multiple comparisons whilst controlling the overall experiment-wise error rate (it is the non-parametric equivalent to the Tukey All-Pairs method). If you don't take account of the number of comparisons then your overall Type I error rate will grow quickly as illustrated below:

-Dave

1 REPLY

- Mark as New
- Bookmark
- Subscribe
- Subscribe to RSS Feed
- Get Direct Link
- Email to a Friend
- Report Inappropriate Content

These are both non-parametric tests so I think they will both work with rank calculations and hence are comparing medians not means. The distinction between the two is that the Wilcoxin test performs pairwise comparisons (it is the non-parametric equivalent of performing a Student's t test on each pair); the alpha level is fixed and takes no account of the number of comparisons being performed. The Steel Dwaas method performs the multiple comparisons whilst controlling the overall experiment-wise error rate (it is the non-parametric equivalent to the Tukey All-Pairs method). If you don't take account of the number of comparisons then your overall Type I error rate will grow quickly as illustrated below:

-Dave