Suppose the z-score of your grade on this statistics exam turns out to be z=0.87. which of the following is the best interpretation of this z
-score?

i answered 87% of the questions correctly.

a. my grade is the 87th percentile.
b. my grade is 0.87 points above the mean.
c. my grade is 0.87 standard deviations above the mean.

c.My grade is 0.87 standard deviations above the mean.

Step-by-step explanation:

given that the  z-score of your grade on this Statistics exam turns out to be z=0.87.

Z score is nothing but std normal variate

Any normal distribution can be converted into std normal by the transformation

Z =

Thus when z=0.87 we mean

x = Mean +0.87 sigma

Or my grade is 0.87 std deviations above the mean

Hence option C is right.

c.My grade is 0.87 standard deviations above the mean.

$450 is the answer.

step-by-step explanation:

30% of 450 = 135

450-135=315