6. A sample of n = 81 from a population of u = 80 and o = 18 has a mean M = 46. What is the o, for the sample means. a. 2 b. 3 C. 6 d. 18 7. A sample of n = 81 from a population of u = 80 and o = 18 has a mean M = 81. What is the z-score for the sample means. a. -.50 b. +.50 c. -1.00 d. +1.00 8. A random sample of n = 36 scores is obtained from a population with a o = 12. If the sample mean is 4 points above the mean, what is the z-score for the sample mean? a. +1.00 b. -1.00 c. +2.00 d. -2.00