Statistical Analyses
hyperalgesia
REGRESSION
All statistical analyses were conducted using the R,To answer the first research question of whether psychological characteristics were related to nocebo hyperalgesia, their univariate relationships were tested using Pearson correlation coefficients, and their multivariate relationships were tested using a multiple regression analysis, where the standardized scores from 6 psychological characteristics were entered to the model as predictors with nocebo hyperalgesia as the outcome variable. For the remaining research questions, a hierarchical regression analysis was conducted to assess the statistical contribution of each block of predictors to the nocebo change score. All continuous predictors were centered around the mean to facilitate the interpretation of interaction effects.To interpret the findings, the model created in step 2 was used for answering the second research question since the global test of this model represents the effect of the single variable entered in that step. For answering the third and fourth research questions, the effect of the global tests of steps 3 and 4, respectively, represent the effect of a group of variables; therefore, to be able to interpret the individual variables and to increase the interpretability of the model, we relied on the final model created with stepwise selection. When these global tests for steps 3 and 4 are significant, applying stepwise selection becomes warranted.