An article in Knee Surgery, Sports Traumatology, Arthroscopy (2005, Vol. 13, pp. 273-279), considered arthroscopic meniscal repair with an absorbable screw. Results showed that for tears greater than 25 millimeters, 13 of 19 repairs were successful while for shorter tears, 23 of 29 repairs were successful. Required:
a. Is there evidence that the success rate is greater for longer tears?
b. Calculate a one-sided 95% confidence bound on the difference in proportions that can be used to answer the question in part (a).