Question

On a recent quiz, the class mean was 72 with a standard deviation of 4.1. Calculate the z-score (to 2 decimal places) for a person who received score of 86. Is a quiz score of 86 considered unusual?Unusual ?Not Unusual?

Answer 1

Answer: Yes, a quiz score of 86 is considered unusual.

Step-by-step explanation:

Given : The class mean : $\mu=72$

Standard deviation : $\sigma=4.1$

Le X be the random variable that represents the scores of student.

The formula of z-score :-

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

For x= 86

$z=\dfrac{86-72}{4.1}=3.41463\approx3.14$

Since the z-score id greater than 1.96 , therefore , it is unusual.