QUESTION 28 A researcher investigates whether or not a new cold medication disrupts mental alertness. It Is known that scores on a standardized test containing a variety of problem-solving tasks are normally distributed with u = 64 and o = 8. An random sample of n = 16 subjects are given the drug and then tested. For this sample, the mean is M 58. Does the medicine have an effect on performance? (test this with a = .01, two-tails) What is the value of the z-test? a. -2.58 b. 2.58 C. 2.00 d. 3.00 QUESTION 29 1 point researcher Investigates whether