The study was designed to detect a
difference of 1 point in pain intensity
in the Pain Numerical Rating Scale
(estimate for standard deviation1.4
points), 1 point in the Patient-
Specific Functional Scale (estimate
for standard deviation1.4 points), 1
point in the Global Perceived Effect
Scale (estimate for standard deviation
1.3 points), and 4 points in
the Roland-Morris Disability Questionnaire
(estimate for standard
deviation4.9 points). The following
specifications were considered:
.05, statistical power of 80%, and
follow-up loss of 15%.