Question

1. the average test grade in mrs. smiths class is 87, with a standard deviation of 4. ahmad made a 90. what is his z - score?

a. 0.75
b. 1.5
c. -1.5
d. -0.75

Explanation:

Step1: Recall z - score formula

The formula for the z - score is $z=\frac{x-\mu}{\sigma}$, where $x$ is the data point, $\mu$ is the mean, and $\sigma$ is the standard deviation.

Step2: Identify values

We are given that $\mu = 87$, $\sigma=4$, and $x = 90$.

Step3: Substitute values into formula

$z=\frac{90 - 87}{4}=\frac{3}{4}=0.75$

Answer:

a. 0.75