A random sample of 13 students were asked how long it took them on certain exam. The mean length of time was 109.3 minutes with a standard deviation...

A random sample of 13 students were asked how long it took them on certain exam. The mean length of time was 109.3 minutes with a standard deviation of 77.6 minutes. Find the lower bound of the 90% confidence interval for the true mean length of time it would take for all students to complete the exam.