Different regression equations relate age to the incidence of Lauren types 1 and 2 stomach cancer in the SEER database: these equations are unaffected by sex or race

Table 7 Comparisons of linear regression models, with and without outlier, of the natural logarithm of the rate of stomach cancer on the main explanatory variables and each of ten interaction variables. The main effects (ME) comprised the explanatory variables five year period, sex, race, Lauren type, and age. The difference between the residual sum of squares (RSS) before and after the addition of each interaction variable to ME (ΔRSS) was divided by RSS and multiplied by error d.f. to yield F, whose numerator df was 1 and denominator df was error df.

WITHOUT OUTLIER
Model Covariates	RSS	ΔRSS	error df	F	P
ME	50.64
ME + five year period:sex	50.60	0.05	152	0.1	0.71
ME + five year period:race	50.09	0.55	152	1.7	0.20
ME + five year period: Lauren type	50.51	0.13	152	0.4	0.53
ME + five year period:age	50.04	0.60	152	1.8	0.18
ME + sex:race	50.62	0.02	152	0.1	0.82
ME + sex:Lauren type	43.99	6.65	152	23.0	3.9 × 10^-6
ME + sex:age	50.63	0.02	152	0.0	0.83
ME + race:Lauren type	45.00	5.64	152	19.0	2.3 × 10^-5
ME + race:age	49.50	1.14	152	3.5	0.06
ME + Lauren type:age	31.62	19.03	152	91.5	< 1 × 10 ^-10
WITH OUTLIER
Model Covariates	RSS	ΔRSS	error df	F	P
ME	58.14
ME + five year period:sex	57.95	0.19	153	0.5	0.48
ME + five year period:race	57.22	0.92	153	2.5	0.12
ME + five year period: Lauren type	57.80	0.34	153	0.9	0.35
ME + five year period:age	57.88	0.25	153	0.7	0.41
ME + sex:race	58.01	0.13	153	0.3	0.57
ME + sex:Lauren type	50.34	7.79	153	23.7	2.8 × 10^-6
ME + sex:age	58.11	0.02	153	0.1	0.81
ME + race:Lauren type	51.44	6.70	153	19.9	1.6 × 10^-5
ME + race:age	57.50	0.63	153	1.7	0.20
ME + Lauren type:age	36.88	21.25	153	88.2	< 1 × 10 ^-10

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