Re: Main and interaction effect in Cox Prop Hazards

Posted by jaycamh on Sep 20, 2019; 4:53pm
URL: http://spssx-discussion.165.s1.nabble.com/Re-Main-and-interaction-effect-in-Cox-Prop-Hazards-tp5738390.html

Hello,

I need help.

I am doing a Cox proportional hazards model in SPSS. I have Low SES and Heavy drinking as 2 main effects and LOW SES x Heavy drinking as interaction effect in the model.

We have stronger (and significant) effects for each main effect but the interaction term is coming protective which is against the theory. Not sure if I am doing it wrong ... see the SPSS result below.

I have, Low SES 0 is reference; 1=low SES

Heavy drinking 0 is reference; 1=heavy drinking.


in fact when I make interaction of alcohol and smoking it’s also coming protective...
Is my Interpretation wrong or is there any other way my syntax should have been formed.

Variables in the Equation
	B	SE	Wald	df	Sig.	Exp(B)	95.0% CI for Exp(B)
							Lower	Upper
AGE	.085	.000	3.719E4	1	.000	1.089	1.088	1.090
SEX - FEMALE	-.433	.013	1.179E3	1	.000	.649	.633	.665
BMI	.001	.001	6.844	1	.009	1.001	1.000	1.003
YEAR	-.006	.002	15.634	1	.000	.994	.990	.997
smoker_cfn			2.716E3	2	.000
smoker_cfn(1)	.827	.016	2.600E3	1	.000	2.285	2.214	2.359
smoker_cfn(2)	.223	.015	221.735	1	.000	1.250	1.214	1.287
heavy_drinker	.566	.110	26.427	1	.000	1.761	1.419	2.186
educ_lowses	.393	.016	608.737	1	.000	1.481	1.436	1.528
heavy_drinker*educ_lowses	-.094	.116	.656	1	.418	.911	.726	1.

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