topic Re: Test difference in slopes in SAS Procedures

Test difference in slopes

ahschnell — Thu, 18 Mar 2021 01:02:01 GMT

Hi. I've run a segmented regression for count data in GENMOD. I created 2 slopes and I want to statistically test the difference between the 2 slopes. Slope1=Slope2 or Slope1-Slope2=0.

I can do this easily in STATA using the lincom command, but I can't figure out how to do it in SAS. TIA

Re: Test difference in slopes

PaigeMiller — Thu, 18 Mar 2021 11:08:35 GMT

Here is an explanation and example: https://support.sas.com/kb/24/177.html

Re: Test difference in slopes

sbxkoenk — Tue, 23 Mar 2021 13:01:19 GMT

Hello @ahschnell ,

Could you solve your "problem" with the suggestion of @PaigeMiller ?

I haven't seen any reaction from your side.

If your question is still alive, you may consider the usage of PROC NLIN (SAS/Stat) for your segmented regression and accompanying hypothesis test.

See:

Segmented regression models in SAS
By Rick Wicklin on The DO Loop
December 14, 2020

https://blogs.sas.com/content/iml/2020/12/14/segmented-regression-sas.html

and

The NLIN Procedure
Example 87.1 Segmented Model
https://go.documentation.sas.com/?cdcId=pgmsascdc&cdcVersion=9.4_3.5&docsetId=statug&docsetTarget=statug_nlin_examples01.htm&locale=en

and

The NLIN Procedure
Example 87.5 Comparing Nonlinear Trends among Groups
https://go.documentation.sas.com/?cdcId=pgmsascdc&cdcVersion=9.4_3.5&docsetId=statug&docsetTarget=statug_nlin_examples05.htm&locale=en

Good luck,
Koen

Re: Test difference in slopes

ahschnell — Tue, 23 Mar 2021 14:05:45 GMT

Thank you both. This is so helpful thank you.