Results indicate that 25 % [standard error (SE) = 0.088] of the variance on the observed scale in initiation is explained by the SNPs. This amount of variance explained collectively by the SNPs is significantly greater than zero [i.e., likelihood ratio test (LRT) (degrees of freedom = 1) = 8.60, P = 0.0016]. The chromosome-by-chromosome heritability analysis indicated that the largest amount of variance in the trait is explained by chromosome 4 (i.e., the estimate on the observed scale equaled 6.8 %, SE = 0.025, LRT(1) = 7.93, P = 0.002). Chromosome 18 accounted for about 3.6 % (SE = 0.01) of the variance on the observed scale in initiation (LRT(1) = 4.99, P = 0.012).
