In a study using 10 samples, and in which the population variance is known, the distribution that should be used to calculate confidence intervals is a standard normal distribution?

Group of answer choices

A) a standard popular distribution.

B) a t distribution with 9 degrees of freedom.

C) a t distribution with 8 degrees of freedom.

D) a z distribution.

An average computer mouse inspector can inspect 37 mice per hour with a population standard deviation of 8 mice per hour. The 50 computer mice inspectors at a particular factory can only inspect 34 mice per hour. Does the company have reason to believe that these inspectors are slower than average at a confidence of 95%? left tailed test.

Group of answer choices

A) Yes, because the test value -5.30 falls in the noncritical region C.V=-1.64.

B) Yes, because the test value -2.65 falls in the critical region to the left of C.V=-1.64.

C) No, because the test value -5.30 falls in the critical region to the left of C.V=-1.28.

D) No, because the test value -3.03 falls in the noncritical region.