8. Nintendo and laparoscopic skills: 42 medical residents were tested on a set of basic laparoscopic skills. 21 were selected at random to undergo systematic Nintendo Wii" training, while the remaining 21 residents were given no Nintendo Wii" training and asked to refrain from video games during this period. The mean improvement in time to complete a gall bladder removal simulation task was 132.2 seconds for the treatment group and 59.7 seconds for the control group. An estimate of the standard error for the difference is 25.4. Source: Basic Practice of Statistics 7E Moore, Fligner. MacMillan press 2015. . Is this an experiment or an observational study? b. Find a 95% confidence interval for the difference in mean improvement times. Assume the sampling distribution is approximately bell-shaped. c. Is it plausible based on the confidence interval that improvement times for an appropriate population are the same for both treatments? Explain. d. Is it reasonable to conclude that Nintendo Wii training caused this difference in improvement times? Explain