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. 2017 Feb 10;18(1):19. doi: 10.1186/s10194-017-0730-5

Fig. 2.

Fig. 2

Path analyses to headache frequency from headache intensity, depression, bodily pain, and burden of headache (physical and emotional) with sleep quality as the mediating variable. Standardized direct path coefficients are presented. Data from double arrows represent correlations between the variables, where data from single arrows represents the standardized regression weight (parameter estimates). e1 and e2: error terms for each variable