The R# Medical Centre undertook a survey to determine the average waiting time of patients in the surgery before they saw a doctor.

The R# Medical Centre undertook a survey to determine the average waiting time of patients in the surgery before they saw a doctor. From 18 responses, the average and standard deviation of the waiting times was found to be 12.3 and 2.03 minutes, respectively. Assuming the information was collected through a random sample and that the waiting time is approximately normally distributed, calculate a 95% confidence interval for the mean waiting time at the medical centre. State the upper bound correct to 3 decimal places.