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 6 Comparisons of linear regression models, with and without outlier, of the natural logarithm of the rate of stomach cancer on the main explanatory variables. The difference between the residual sum of squares (RSS) before and after each explanatory variable had been added to regression (ΔRSS) was divided by RSS and multiplied by the error df to yield F, whose numerator df was 1 and denominator df was the error df.

WITHOUT OUTLIER
Model Covariates	RSS	ΔRSS	error df	F	P
Null	403.26
five year period	402.96	0.30	157	0.1	0.73
five year period + sex	388.32	14.64	156	5.9	0.02
five year period +sex + race	319.23	69.09	155	33.5	3.8 × 10^-8
five year period + sex + race + Lauren type	255.93	63.30	154	38.1	5.7 × 10^-9
five year period + sex + race + Lauren type + age	50.64	205.29	153	620.2	< 1 × 10 ^-10
WITH OUTLIER
Model Covariates	RSS	ΔRSS	error df	F	P
Null	437.81
five year period	436.79	1.02	158	0.4	0.54
five year period + sex	418.50	18.29	157	6.9	0.01
five year period +sex + race	342.38	76.12	156	34.7	2.3 × 10^-8
five year period + sex + race + Lauren type	273.23	69.15	155	39.2	3.5 × 10^-9
five year period + sex + race + Lauren type + age	58.14	215.10	154	569.8	< 1 × 10 ^-10

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