High levels of cholesterol in the blood increase the risk of heart disease. For 14-year-old boys, the
distribution of blood cholesterol is approximately Normal with a mean of 170 milligrams of cholesterol per
deciliter of blood (mg/dl) and a standard deviation of 20 mg/dl. Which equation could be used to solve for the 30ª
percentile of this distribution?
a) -0.30 = x-170
20
b) 0.30: x-170
20
c) -0.52
d) 0.52 = x-170
20
e) 0.30
=
x-170
20
170-x
20
0542