Question 8 0/1 pt 9 3 7 A researcher is interested in finding a 90% confidence interval for the mean number minutes its students are concentrating on their professor during a one hour statistics lecture. The study included 138 students who averaged 34.3 minutes concentrating on their professor during the hour lecture. The standard deviation was 11.7 minutes. a. To compute the confidence interval use a ? distribution. b. With 90% confidence the population mean minutes of concentration is between (round to 3 decimal places) and minutes. c. If many groups of 138 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 percent will not contain the true population mean minutes of concentration. Hint: Hints Video Textbook