Scoliosis is a condition involving curvature of the spine. In a study by A. Nachemson and L. Peterson, reported in the Journal of Bone and Joint Surgery (Vol. 77, Issue 6, pp. 815-822), 286 girls aged 10 to 15 years, were followed to determine the effects of observation only (129 patients), an underarm plastic brace (111 patients), and nighttime surface electrical stimulation (46 patients). A treatment was deemed to have failed if the curvature of the spine increased by 6◦ on two successive examinations. The preceding table summarizes the results obtained by the researchers. At the 5% significance level, do the data provide sufficient evidence to conclude that a difference in failure rate exists among the three types of treatments?
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