5. The use of patients with a variety of diagnoses, and therefore heterogeneous painful stimuli, risks masking a treatment effect because of large inter-individual variability. There are several design and analytic factors (detailed below) that attenuate this risk: 1) a sufficiently large number of patients will be randomly assigned to each group so that the variety of painful stimuli will be equally distributed between treatment groups; 2) change in pain intensity and pain relief will be analyzed rather than absolute pain intensity or pain relief therefore reducing variability.