Table II.

Analysis of variance of serum TTR levels, with factors sex, race and age.

Source	Sum-of- squares	df	Mean- square	F-ratio	p
Sex	0.266	1	0.266	30.725	< 0.001
Race	0.072	1	0.072	8.293	0.004
Age	0.059	1	0.059	6.837	0.009
Race*sex	0.004	1	0.004	0.463	0.496
Age*sex	0.030	1	0.030	3.440	0.064
Age*race	0.000	1	0.000	0.011	0.915
Error	14.141	1636	0.009

Sex (female vs. male), race (African-American (814) vs. Caucasian (828)) and age (< 60 years old vs. 60 or older) are categorical variables in this analysis of variance. The p-values correspond to the F-statistics for the main effects (sex, race and age) and the first-order interactions (race*sex, age*sex and age*race).