GIVEN
The mean of the distribution is 75% with a standard deviation of 8%. Edna scores 85% on the test.
SOLUTION
The z-score can be used to get the percentage that Edna's score falls into. The formula is given to be:
[tex]z=\frac{x-\overline{x}}{\sigma}[/tex]
From the information provided, the following parameters can be substituted into the formula:
[tex]\begin{gathered} x=85 \\ \overline{x}=75 \\ \sigma=8 \\ \therefore \\ z=\frac{85-75}{8}=\frac{10}{8}=1.25 \end{gathered}[/tex]
Using tables, the score corresponds to 89.44% of her class.
Therefore, Edna doesn't rank in the top 10% of her class because approximately 10.6% of the class scored bove her.
OPTION D is the correct option.
