The test scores for the verbal reasoning and the quantitative reasoning sections of the Graduate Record Examination (GRE) are normally distributed. In a recent year, the mean test score was 150 and the standard deviation was 8.75.
The test score for Student A was 162.
The test score for Student B was 168.
The test score for Student C was 155.
The test score for Student D was 138.
What is the z-score for each student and are any of the students scores considered statistically unusual? If so, explain your reasoning. Be sure to label your z-score with each student's letter.