Question

According to a factory employer, the mean working time of workers in 

the factory is 6 hours with a standard deviation of 0.5 hours

Answer 1

Null hypothesis: The mean working time for the workers in the factory is 6 hours.

Alternative hypothesis: The mean working time for the workers in the factory is not 6 hours.

$H_0:\mu=6$

$H_1:\mu\not=6$

This corresponds to a two-tailed test, for which a z-test for one mean, with known population standard deviation will be used.