topic Linear regression comparison between groups in Statistical Procedures

Linear regression comparison between groups

lauramb — Thu, 11 Jan 2018 23:27:05 GMT

Hi everyone I'm new to SAS so my question may be quite basic:

I have a blood test result (y) that follows the following relationship with a drug concentration (x):

Y = B0 + B1*X**0.5

As I understand this is a linear relationship for the parameters (https://support.sas.com/documentation/cdl/en/statug/63033/HTML/default/viewer.htm#statug_nlin_sect003.htm) so the regression should be done using a linear regression model.

I have used proc reg but with linear Y functions.

As I understand the code for the linear regression is:

  proc reg data=dataser;
      var X**0.5;
      model Y=X;
   run;

Is that correct?

If I have the data of two groups (patients vs control) how can I compare the regression coefficients for both groups?

Thanks for your help

Re: Linear regression comparison between groups

Ksharp — Fri, 12 Jan 2018 13:19:38 GMT

Add one more data step to get

data dataser;
 set dataser;
 X=sqrt(X);
run;
proc reg data=dataser;
      model Y=X;
quit;

Re: Linear regression comparison between groups

PaigeMiller — Fri, 12 Jan 2018 14:12:00 GMT

@lbelluscio wrote:

If I have the data of two groups (patients vs control) how can I compare the regression coefficients for both groups?

proc glm data=dataser;
      class group;
      model Y=group x x*group;
quit;

If the variable group is not statistically significant when you perform this regression, then the intercepts of the two groups are not significantly different. If the interaction x*group is not statistically significant when you perform this regression, then the slopes of the two groups are not significantly different.

Re: Linear regression comparison between groups

StatDave — Fri, 12 Jan 2018 16:23:39 GMT

See this note for more on the general topic of comparing models fit to multiple groups.

Re: Linear regression comparison between groups

lauramb — Fri, 12 Jan 2018 20:12:37 GMT

Thanks all for your help!