A researcher is interested in finding a 93% confidence interval for the mean number minutes students are concentrating on their professor during a one hour statistics lecture. The study included 138 students who averaged 313.: minutes concentrating on their professor during the hour lecture. The standard deviation was 12.5 minutes. Round answers to 3 decimal places where possible. a. To compute the confidence interval use a distribution. b. With 93% confidence the population mean minutes of concentration is between C] and :1 minutes. c. If many:r groups of 138 randomlyr selected members are studied, then a different confidence interval would be produced from each group. About :1 percent of these confidence intervals will contain the true population mean minutes of concentration and about :1 percent will not contain the true population mean minutes of concentration