Overall analytical strategy
headache
A series of potential treatment effect modifiers was identified based on the existing literature on headache characteristics and risk factors for headache in children. In addition, an expected benefit index was created based on most and least favourable conditions for a benefit from chiropractic treatment. These conditions reflected the expectations of the principal investigator (SL), based on her clinical experience.For the confirmative part, the identified potential effect modifiers led to a series of candidate variables based on the baseline data available. The expected benefit index was also considered as a candidate variable. The modifying effect of each candidate variable was examined by considering the difference in the primary outcomes between the two intervention groups, stratified by the values of the candidate variables, and assessing the statistical significance of this association.In the exploratory part, an attempt was made to construct a new index variable by combining all single candidate variables The potential value of this new index was depicted in the same manner as for the candidate variables, except for the statistical significance of the association, which could not be assessed.