Question

The distribution of cholesterol levels in teenage boys is approximately normal with µ = 170 and σ = 30. Levels above 200 warrant attention. What percentage of teenage boys have levels between 140 and 230? (Use Empirical Rule)?*

Answer 1

We want to find the P(140 < x < 230)

To do so we find the z scores associated with both 140 and 230.

z= (x-µ)/σ

z1= (140-170)/30 = -1

z2= (230-170)/30 = 2

Applying the empirical rule, we get:

The percentage of teenage boys that have levels between 140 and 230 will be:

`\text{ 34\% + 34\% + }13.5\text{\%}`
`\text{ = }81.5\text{\%}`

Therefore, the answer is 81.5%.