Question

19) The distribution of cholesterol levels in teenage boys is approximately normal with u = 170 and o=30 (Source: U.S. National Center for Health Statistics). Levels above 200 warrant attention. What percent of teenage boys have levels between 170 and 225? A) 56.13% B) 3.36% C) 46.64% D) 6.06%

Answer 1

Solution :

Given that ,

mean = $\mu$ = 170

standard deviation = $\sigma$ = 30

P(170< x < 225) = P[(170 - 170) /30 < (x - $\mu$ ) / $\sigma$ < (225 - 170) /30 )]

= P(0 < Z <1.83 )

= P(Z <1.83 ) - P(Z < 0)

Using z table   

= 0.9664 -0.5

=0.4664

answer=46.64%