 Stroke is a leading cause of neurological disability worldwide, often causing significant weakening and paresis of the affected arm. National spending on post-stroke rehabilitation is project to expand 20 to 35 through 2010. As a new tool for therapists, robotic stroke therapy devices have the potential to be a cost-effective device aid to physical therapy and enable novel modes of exercise not currently available. While recent studies have shown chronic patients benefit from repetitive practice, it is not clear whether they improved via a reduction in impairment or increased functional compensation because there is a lack of standard treatment and scales to assess rehabilitation efficacy in chronic stroke patients. This study aims to reconcile difference performance measurements in robotic rehabilitation to assess the outcome of robotic rehabilitation training. 