Question: Over several years a foreman kept records of how long it took assembly line workers to assemble a unit. He found that workers required an average time of only 15 minutes and standard deviation of 1.5 minutes of completion. A random sample of 64 workers from night shift was timed and found an average of 16.4 minutes. Construct a 95% confidence interval for the average time of completion for night-shift workers based on the above sampling information.