Statistical Analyses
depression, fatigue, anxiety, pain
REGRESSION
Baseline characteristics, usefulness, ease of use, and user patterns were summarized with means and SDs for normally distributed variables and medians and ranges for variables with skewed distributions. The type of distribution was assessed using the visual inspection of histograms and q-q plots and by comparing means and medians. Categorical data were presented as counts and percentages. Change scores, defined as a difference between scores at baseline and at 3 months, were calculated for pain interference, anxiety, depression, self-regulatory fatigue, HRQoL, pain catastrophizing, and pain acceptance and used as dependent variables in linear regression models. As statistically significant differences were observed between the intervention and care-as-usual control groups for age and years living with pain, these variables were included in the intention-to-treat analysis as possible confounders. We included only individuals with data on both assessment points; thus, there were no missing data and no imputation of missing values was necessary. Model fit was tested using visual inspection of the residual plots of histograms, and the model fit was satisfactory for all the presented variables (ie, change scores). 