You find out that the average 10th grade math score, for Section 6 of the local high school, is 87 for the 25 students in the class. The average test score for all 10th grade math students across the state is 85 for 1,800 students. The standard deviation for the state is 3.8.

Answer the following questions:

What z score do you calculate?
What is the area between the mean and the z score found in Appendix A of the textbook?
What does this mean about the probability of this test score difference occurring by chance? Is it less than 0.05?

1 answer

Z = (score-mean)/SD

This should give you a good start:

Z = (mean1 - mean2)/standard error (SE) of difference between means

SEdiff = √(SEmean1^2 + SEmean2^2)

SEm = SD/√n