The time taken for a sample of eight pieces of equipment to do a task has a mean of 52 minutes and a standard deviation of 18 minutes. What is the 90% confidence interval for the mean time of all the equipment to do the task? What is the 95% confidence interval? If the same results had been found from a sample of 20 pieces of equipment, what would be the 95% confidence interval? What would be the result if a Normal distribution had been used?