9.

You intend to estimate a population mean / with the following sample. 86.5 73 84.1 77.7 84.9 79.3 87.4 84.4 67.5 86.1 69 You believe the population is normally distributed. Find the 9% confidence interval. Enter your answer as an open-interval (i.e., parentheses) accurate to two decimal places (because the sample data are reported accurate to one decimal place). 99% C.I. = Answer should be obtained without any preliminary rounding