Question

What is the z-score of sample X, if `n = 100, mu= 45, SD =30, and E[X] =31`?

Answer 1

The z-score is `=-5`

Explanation:

The z-score for a sample mean is

`z=(barx-mu)/(sigma/sqrtn)`

`barx=E [X] =31`

`mu=45`

`sigma=30`

`n=100`

`z=(31-45)/(30/sqrt100)=(-15)/(3)=-5`