topic Re: Phreg multivariable model - hazard ratio is 1 and significant in Statistical Procedures

Phreg multivariable model - hazard ratio is 1 and significant

SAS_User — Sun, 22 Jan 2017 02:06:47 GMT

I ran a Proc phreg with 2 continuous variables and 3 binary variables. One of the continuous variables (ranges between 10 and 250) is highly significant but the HR is only 1.013. This is from the "Analysis of Maximum Likelihood Estimates" table.

Any thoughts on what might cause such results? I have a reasonable sample size of 150 observations. The binary variables have a distribution of <10 yeses and 140 "no"s

Re: Phreg multivariable model - hazard ratio is 1 and significant

mkeintz — Sun, 22 Jan 2017 05:00:44 GMT

Why is a hazard ratio of 1.013 particularly small for a continuous variable thet ranges from 10 to 250? The HR is presumably for a 1 unit change in the variable (e.g. from 10 to 11). So a 10-unit change has an HR of 1.1378, and the full range of 240 units has an HR of 22.195. Is that disappointingly low?

Re: Phreg multivariable model - hazard ratio is 1 and significant

SAS_User — Sun, 22 Jan 2017 06:00:14 GMT

Thank you very much for your explanation. My HR is actually exactly 1 for a variable that ranges from .1 to 1600. Would that be just displayed that way due to rounding? How can I explain that? Thanks

Re: Phreg multivariable model - hazard ratio is 1 and significant

SAS_User — Sun, 22 Jan 2017 06:02:27 GMT

It's 1.000 to be exact

Re: Phreg multivariable model - hazard ratio is 1 and significant

JacobSimonsen — Sun, 22 Jan 2017 09:49:48 GMT

I think you should scale your contionous variable such that the variable you put into PHREG goes in from 0 to 10 (or of that order of magnitude).Otherwise rounding errors and errors due to numerical precision otherwise can easily get a too big impact on the interpretation of the estimates.

Re: Phreg multivariable model - hazard ratio is 1 and significant

SAS_User — Mon, 27 Feb 2017 19:56:14 GMT

Thank you for the suggestion. That was very helpful