Contributor
Posts: 29

# hazard ratio from regression coefficients in an interaction term

[ Edited ]

I am using proc phreg to estimate hazard ratios, my model is as follows:

time*event(0) = week|avg education race;

random zipcode;

I would like to get the hazard ratio for 'week'. I was originally doing this by hand by summing the estimate from week and the interaction term, but assume there is a way to do this using estimate/contrast?

Thank you!

Super User
Posts: 23,705

## Re: hazard ratio from regression coefficients in an interaction term

Try a HAZARDRATIO statement instead. Much simpler syntax.

Regular Contributor
Posts: 159

## Re: hazard ratio from regression coefficients in an interaction term

youdont have week as a main factor in the model, just in the interaction? you'll need to use 'at' in the hazardratio statement @Reeza suggested, see here: https://support.sas.com/documentation/cdl/en/statug/63033/HTML/default/viewer.htm#statug_phreg_sect0...

--------------
blog: papersandprograms.com
Contributor
Posts: 29

## Re: hazard ratio from regression coefficients in an interaction term

When I use the hazardratio statement I cannot recreate what I get when I am summing the coefficients by hand. This is why I wasn't using it initially - is there a specification that needs to be made?

Example:

 Estimate Exp summed estimate Hazard Ratio from SAS average 0.000196 0.999763628 0.995 week -0.0002121 week*average -0.0000243
Regular Contributor
Posts: 159

## Re: hazard ratio from regression coefficients in an interaction term

are you doing it by hand or in a data step? it could be rounding error, calculate the hr in a data step as exp(estimate). Also did you use 'at' in the hazard ratio statement? if you just sum them up then it's at average=1?

--------------
blog: papersandprograms.com
Super User
Posts: 23,705

## Re: hazard ratio from regression coefficients in an interaction term

99% of the time the error is with the hand calculation.

Do it with a data step so you can't get any typo's or rounding errors and post your code if it still doesn't match.

Discussion stats
• 5 replies
• 115 views
• 0 likes
• 3 in conversation