In a local community, assume ages are normally distributed with a standard deviation of 10. in order to estimate the average age of people in the community, a sample of 25 people are taken. the mean of these sample values is 54. the upper bound of the 90% confidence interval for the mean age is 57.3. what is the lower bound for the 90% confidence interval?

Industrial engineers who specialize in ergonomics are concerned with designing workspace and devices operated by workers so as to achieve high productivity and comfort. a paper published in this research area reports on a study of preferred height for an experimental keyboard with large forearm-wrist support. a sample of 31 trained typists resulted in an average preferred height of 80.0 cm