18. A random sample of 16 statistics examinations from a large population was taken. The average score in the sample was 78.6 and population variance was 64. We are interested in determining whether...

18. A random sample of 16 statistics examinations from a large population was taken. The average score in the sample was 78.6 and population variance was 64. We are interested in determining whether the average grade of the population is at least 75. Assume the distribution of the population of grades is normal. Then the critical value of the test at 5% level is A. -1.645 B. None C. 1.96 D. 1.645 E. 1.753