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The annual salaries of all employees at a financial company are normally distributed with a mean [tex]\(\mu=\$34,000\)[/tex] and a standard deviation [tex]\(\sigma=\$4,000\)[/tex]. What is the [tex]\(z\)[/tex]-score of a company employee who makes an annual salary of [tex]\(\$28,000\)[/tex]?

A. [tex]\(-5\)[/tex]
B. [tex]\(-3.5\)[/tex]
C. [tex]\(-1.5\)[/tex]
D. 1.5


Sagot :

Sure, let me guide you through the process of finding the z-score step-by-step.

The z-score measures how many standard deviations an element is from the mean. It is calculated using the formula:

[tex]\[ z = \frac{X - \mu}{\sigma} \][/tex]

where:
- [tex]\( X \)[/tex] is the value in the distribution (in this case, the employee's salary),
- [tex]\( \mu \)[/tex] is the mean of the distribution,
- [tex]\( \sigma \)[/tex] is the standard deviation of the distribution.

Given:
- The mean salary [tex]\(\mu = \$34,000\)[/tex],
- The standard deviation [tex]\(\sigma = \$4,000\)[/tex],
- The employee's salary [tex]\(X = \$28,000\)[/tex].

Now, we plug these values into the z-score formula:

1. Subtract the mean from the employee's salary:
[tex]\[ X - \mu = 28,000 - 34,000 = -6,000 \][/tex]

2. Divide this result by the standard deviation:
[tex]\[ z = \frac{-6,000}{4,000} = -1.5 \][/tex]

Therefore, the z-score of a company employee who makes an annual salary of $28,000 is [tex]\(-1.5\)[/tex].

So the correct answer is [tex]\(-1.5\)[/tex].