The distribution of cholesterol levels in teenage boys is approximately normal with $\mu$ = 170 and $\sigma$ = 30 (Source: U.S. National Center for Health Statistics). Levels above 200 warrant attention. Find the probability that a
Teenage boy has a cholesterol level greater than 225.
A)0.0336
B)0.0606
C)0.0718
D)0.0012

Question

Quizplus · Accepted Answer

To find the probability that a teenage boy has a cholesterol level greater than 225, we use the Z-score formula: $Z = \frac{X - \mu}{\sigma}$, where $X$ is the value of interest (225), $\mu$ is the mean (170), and $\sigma$ is the standard deviation (30). Plugging in the values, we get $Z = \frac{225 - 170}{30} = \frac{55}{30} = 1.8333$. Looking up this Z-score in a standard normal distribution table or using a calculator, we find the probability associated with a Z-score greater than 1.8333 is approximately 0.0336.

The Distribution of Cholesterol Levels in Teenage Boys Is Approximately μ\muμ

The Distribution of Cholesterol Levels in Teenage Boys Is Approximately $\mu$