highly significantp -value < 2 × 10 −16
The analysis of variance (ANOVA) results (Supplementary Data 1 –Table B 3 ) showed a highly significant effect of landmarks on measurement variance ( p -value < 2 × 10 −16 ); however, no significant effect of the operator ( p -value = 1.00) or the interaction between landmark and operator was observed ( p -value = 0.968).