2.11. Statistical Analysis
mean stiffness, SD stiffness
REGRESSION
With 100 patients in each group, we had 0.99 power to detect a significant difference within each of the four groups immediately and 24 h after treatment. For between-group comparisons, we had at least 0.98 power to detect a 10 mm minimum clinically significant difference in stiffness VAS score [Baseline characteristics were analyzed using Fisher’s exact test (gender and duration of stiffness); one-way ANOVA (mean stiffness and mean age); and Levene’s test (SD stiffness and SD age).A mixed-model regression was fit with stiffness a response and patient as a random effect. The fixed effects in this model were age, gender, duration, stiffness, group, and time, and all two- and three-factor interactions involving the last three of these covariates. Post hoc pairwise comparisons of group and times were performed to compare the effects of different interventions/conditions. The chi-squared test was used to compare numbers of improved patients among the four groups.To evaluate the blinding effect, the mixed model was fit to data from each group separately (except no-treatment control), with stiffness as the response, participant as random effect, and covariates age, gender, stiffness duration, patient (or practitioner) guess, and time, as well as the two- and three-factor interactions of stiffness duration, patient guess, and time. The chi-squared test of goodness-of-fit was used to determine whether the proportions of penetrating, skin-touch, and no-touch in the patients guessed at each treatment were the same. The Kruskal–Wallis test was used to detect significant differences among the three treatment groups in the confidence levels of practitioners and patients guesses.