The scores of an eighth-grade math test have a normal distribution with a mean [tex]\mu = 83[/tex] and a standard deviation [tex]\sigma = 5[/tex]. If Din's test score was 92, which expression would she write to find the [tex]z[/tex]-score of her test score?

A. [tex]z = \frac{92 - 83}{83}[/tex]
B. [tex]z = \frac{83 - 92}{5}[/tex]
C. [tex]z = \frac{92 - 83}{5}[/tex]
D. [tex]z = \frac{5 - 83}{92}[/tex]



Answer :

To determine which expression Din should use to find the [tex]$z$[/tex]-score of her test score, we first need to recall the formula for calculating a [tex]$z$[/tex]-score. The [tex]$z$[/tex]-score is a way of describing how far a particular score is from the mean in terms of standard deviations.

The formula for the [tex]$z$[/tex]-score is given by:
[tex]$ z = \frac{x - \mu}{\sigma} $[/tex]
where:
- [tex]\( x \)[/tex] is the value of the score,
- [tex]\( \mu \)[/tex] is the mean,
- [tex]\( \sigma \)[/tex] is the standard deviation.

Given:
- [tex]\( \mu = 83 \)[/tex],
- [tex]\( \sigma = 5 \)[/tex],
- [tex]\( x = 92 \)[/tex].

Now, substitute these values into the formula:
[tex]$ z = \frac{92 - 83}{5} $[/tex]

Thus, the correct expression Din should use to find the [tex]$z$[/tex]-score of her test score is:
[tex]$ z = \frac{92 - 83}{5} $[/tex]

Choosing the correct option:
[tex]$ z = \frac{92 - 83}{5} $[/tex]