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
- :
- Problem with Parameter Estimates in a Regression I...

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

May 27, 2017 11:15 PM
(1831 views)

Hello! I am having difficulty looking into what drives an interaction I have found. The interaction is between Age and Group. Since Age is a continuous variable, I have used a regression to look into it. I would like to do individual t-tests within the regression to see what is driving the interaction. I believe this would be under the "Parameter Estimates" section of the report.

However, for whatever reason, JMP does not include all three groups in the Parameter Estimates. It always seems to leave out a group. I tried the model with groups A, B, and C, and it gave me estimates for A and B. When I tried it with just groups B and C, it only gave me estimates for B. And when I tried groups A and C, it again only gave me estimates for A. Why is this? Can anybody help me? Thank you!

1 ACCEPTED SOLUTION

Accepted Solutions

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

May 28, 2017 6:28 AM
(3639 views)

Solution

The mathematics requires that one group be omitted since an observation that does not belong to any of the other groups must belong to that particular group (rendering the matrix noninvertable). In order to see all the regresssion coefficients, click on the red triangle at the top of the model output and ask for the Expanded Estimates and it will show the coefficients for all the groups (the missing group coefficient is always equal to 0 - sum of the other coefficients).

2 REPLIES

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

May 28, 2017 6:28 AM
(3640 views)

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

May 28, 2017 11:35 AM
(1812 views)

That was exactly what I was looking for. Thank you so much for the help and the explanation!