Answer: Yes, a quiz score of 86 is considered unusual.
Step-by-step explanation:
Given : The class mean : [tex]\mu=72[/tex]
Standard deviation : [tex]\sigma=4.1[/tex]
Le X be the random variable that represents the scores of student.
The formula of z-score :-
[tex]z=\dfrac{x-\mu}{\sigma}[/tex]
For x= 86
[tex]z=\dfrac{86-72}{4.1}=3.41463\approx3.14[/tex]
Since the z-score id greater than 1.96 , therefore , it is unusual.
