Table 4 ANCOVA results for Brain Age Gap calculated for each regressor trained. Normality and equality of variances were tested before applying the ANCOVA. Sex and eTIV were included as covariates. The \(\eta _p^2\) effect sizes were small (\(\eta _p^2 < 0.06\)) for all comparisons. Statistically significant elements are shown in bold

Combined Feature Set

F-value

1.734

6.796

1.110

Effect size (\(\varvec{\eta }_{\varvec{p}}^{\varvec{2}}\))

0.012

0.043

0.007

p-value

0.190

0.010

0.294

Morphological Feature Set

F-value

0.102

3.237

1.924

Effect size (\(\varvec{\eta }_{\varvec{p}}^{\varvec{2}}\))

< 0.001

0.021

0.012

p-value

0.750

0.074

0.167

Intensity Feature Set

F-value

1.802

4.094

0.336

Effect size (\(\varvec{\eta }_{\varvec{p}}^{\varvec{2}}\))

0.011

0.026

0.002

p-value

0.181

0.045

0.563