50. The paint used to make lines on roads must re ect enough light to be clearly visible at night. Let m denote the true average re ectometer reading for a new type of paint under consideration. A test of H0:

m20 versus Ha: m 20 will be based on a random sample of size n from a normal population distribution.

What conclusion is appropriate in each of the following situations?

a. n  15, t  3.2, a  .05

b. n  9, t  1.8, a  .01

c. n  24, t.2