Question

NEED HELP
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 student’s test grade was 91. What is the z-score for the student’s test?

–5.20
–2.60
2.60
5.20

Answer 1

Answer:

2.60

Step-by-step explanation:

z-score is the difference between the score and mean, divided by the standard deviation.

$z = \frac{x - \mu}{\sigma}$

$z = \frac{91-77.5}{5.2} = \frac{13.5}{5.2} \approx 2.596$

So 2.6 is an answer close enough.