Below are the arithmetic test scores of Ms. Teachwell's fourth-grade class. The statewide average on this same test for all fourth graders is 77.0. The statewide standard deviation is 7.0. You want to know if the performance of Ms. Teachwell's class is typical of the state's fourth graders.

a. State the null hypothesis.
b. Calculate the normal deviate Ztest. (Note: To do this, you will need to find the mean for Ms. Teachwell's class and the GM for a sample of this size.)
c. What is the probability that Ms. Teachwell's class would score at least as high as it did if her class were just a random fourth-grade class from across the state?
d. The principal commends Ms. Teachwell for the outstanding performance of her class. Review: What factors other than her exceptional teaching ability might explain the performance of Ms. Teachwell's class? Give explanations in terms of (i) random error and (ii) confounding variables.

Transcribed Image Text:

72 91 74 83 94 75 89 82 73 67 82 83 79 82 82 80 81 92 80 70 74 78 92 81 75 76 90 72 77 68