An insurance company employs agents on a commission basis. It claims that in their first-year agents will earn a mean commission of at least $40,000 and that the population standard deviation is no...

An insurance company employs agents on a commission basis. It claims that in their first-year agents will earn a mean commission of at least $40,000 and that the population standard deviation is no more than $6,000. A random sample of nine agents found for commission in the first year,

where xi is measured in thousands of dollars and the population distribution can be assumed to be normal. Test, at the 5% level, the null hypothesis that the population mean is at least $40,000.