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 136 students who averaged 40.3 minutes concentrating on their professor during the hour lecture. The standard deviation was 12.5 minutes. a. To compute the confidence interval use a ? v 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 136 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 D