The value of the z-score is -1.4.
Given that
A normal distribution of data has a mean of 90 and a standard deviation of 18.
We have to determine
What is the approximate z-score for the value 64?
According to the question
The z-score is determined by the following formula given below;
[tex]\rm Z-score = \dfrac{x-Mean}{Standard \ deviation}[/tex]
A normal distribution of data has a mean of 90 and a standard deviation of 18.
And the value of x is 64.
Therefore,
The value of the z-score is,
[tex]\rm Z-score = \dfrac{x-Mean}{Standard \ deviation}\\\\\rm Z-score = \dfrac{64-90}{18}\\\\\rm Z-score = \dfrac{-26}{18}\\\\\rm Z-score = -1.4[/tex]
Hence, the value of the z-score is -1.4.
To know more about Z-score click the link given below.
https://brainly.com/question/795909
