Table 3. Correlation between variables of effective helmet therapy and starting age (month), by the Spearman rank correlation test.

Variables	Spearman's coefficient of rank correlation, rho	95% CI for rho	P valuea
Absolute diagonal distance difference, mm	−0.520	−0.718, −0.245	< 0.001
CVAI change, %	−0.522	−0.719, −0.247	< 0.001
Absolute diagonal distance difference velocity, mm/day	−0.568	−0.749, −0.307	< 0.001
Absolute diagonal distance difference velocity, mm/mon	−0.568	−0.749, −0.307	< 0.001
CVAI change velocity, %/day	−0.451	−0.671, −0.159	< 0.001
CVAI change velocity, %/mon	−0.586	−0.761, −0.332	< 0.001

CI = confidence interval, CVAI = cranial vault asymmetry index.

^aStatistically significant P < 0.05.