A researcher is interested in finding a 90% confidence interval for the mean number minutes students are concentrating on their professor during a one hour statistics lecture. The study included 137 students who averaged 39.8 minutes concentrating on their professor during the hour lecture. The standard deviation was 10.4 minutes. Round answers to 3 decimal places where possible. a. To compute the confidence interval use a distribution. b. With 90% confidence the population mean minutes of concentration is between and minutes. c. If many groups of 137 randomly selected members are studied, then a different confidence interval would be produced from each group. About percent of these confidence intervals will contain the true population mean minutes of concentration and about contain the true population mean minutes of concentration. percent will not