On a unit test in a statistics class, the teacher determines that the mean test grade was 77.5 with a standard deviation of 5.2. One test grade has a z-score of 2.4. Which of the following statements gives the best interpretation of this z-score?
Answer
A
This student’s test grade was higher than 2.4% of the other students’ test grades.
B
This student’s test grade was 2.4 standard deviations above the mean test grade.
C
This student’s test grade was 2.4 standard deviations below the mean test grade.
D
The student’s test grade was lower than 2.4% of the other students’ test grades.
Explanation
A z-score tells how many standard deviations a value is from the mean. Since the z-score is positive, the grade is above the mean; a z-score of 2.4 means it is 2.4 standard deviations above the mean. Therefore, the best interpretation is that the student’s test grade was 2.4 standard deviations above the mean test grade.
AI-written and checked against the verified answer.