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.

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=(x-\mu)/(\sigma)`

For x= 86

`z=(86-72)/(4.1)=3.41463\approx3.14`

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