Question

4. Radical cystectomy is the standard management of nonmetastatic, invasive bladder cancer. However, this treatment was associated with clinically significant perioperative complications and prolonged recovery time among patients with this disease, who are typically older and often have a history of smoking and coexisting conditions. Retrospective studies indicated that robot-assisted laparoscopic surgery was associated with a reduced risk of complications and shorter hospital stay, as compared with open surgery, but data was lacking from randomized trials. Memorial Sloan Kettering Cancer Center reported the results of a randomized, controlled trial (ClinicalTrials.gov number, NCT01076387), just recently, in the NEJM, on July 23, 2014, designed to assess whether robot-assisted laparoscopic radical cystectomy (n=29) would be associated with a lower rate of perioperative complications as compared to open surgery (n=28). No differences were found in complication rates or Length of Stay (LOS). However, regarding operating-room time in minutes, the following was found (mean ± SD):4. Radical cystectomy is the standard management of nonmetastatic, invasive bladder cancer. However, this treatment was associated with clinically significant perioperative complications and prolonged recovery time among patients with this disease, who are typically older and often have a history of smoking and coexisting conditions. Retrospective studies indicated that robot-assisted laparoscopic surgery was associated with a reduced risk of complications and shorter hospital stay, as compared with open surgery, but data was lacking from randomized trials. Memorial Sloan Kettering Cancer Center reported the results of a randomized, controlled trial (ClinicalTrials.gov number, NCT01076387), just recently, in the NEJM, on July 23, 2014, designed to assess whether robot-assisted laparoscopic radical cystectomy (n=29) would be associated with a lower rate of perioperative complications as compared to open surgery (n=28). No differences were found in complication rates or Length of Stay (LOS). However, regarding operating-room time in minutes, the following was found (mean ± SD):

Robot-Assisted Surgery	Open Surgery
n=29	n=28
456 ± 82 min	329 ± 77 min

NOTE: Assume all data is approximately normally distributed. Assume the variances of 2 groups are equal. To test by hypothesis whether there is a difference in group mean operating-room times between the 2 groups, write down the appropriate information below: You do not need to solve this calculation.

a. null and alternate hypothesis:

b. Test-statistic you would use.

c. Should we be concerned with degrees of freedom here? Circle one: Yes/No

d. If the answer is yes, how many are there? ____________

e. What would the critical value be for this test if alpha is set at 0.05? _________________

Answer 1