1.The serum cholesterol (SC) levels of 12-to-14-year-olds follow a normal distri

We have to use R a. P(Xmu+sigma) = pnorm(1) = .8413 c. P(mu-sigma

ID: 3330208 • Letter: 1

Question

1.The serum cholesterol (SC) levels of 12-to-14-year-olds follow a normal distribution with mean 155 mg/dl and standard deviation 27 mg/dl.

Using R calculate the following:

A. Find the percentage of 12-to-14-year-olds with SC levels less than -

B. Find the percentage of 12-to-14-year-olds with SC levels more than +

C.What is the percentage of 12-to-14-year-olds with SC levels between - and + ?

D.What is the percentage of 12-to-14-year-olds with SC levels between - 2 and + 2

E.What is the percentage of 12-to-14-year-olds with SC levels between -3 and +3

2.Using R and Z-table.

Find the 80th percentile ("The SC level that is higher than 80% of all 12- to-14-year-olds") (In terms of the problem, meaning in mg/dl)

3. Using R and Z-table. Find the 20th percentile (In terms of the problem)

We have to use R

a. P(X<mu-sigma) = pnorm(-1) = .1587

b. P(X>mu+sigma) = pnorm(1) = .8413

c. P(mu-sigma<X<mu+sigma) = pnorm(1)-pnorm(-1) = .68

d. P(mu-2sigma<X<mu+2sigma) = pnorm(2)-pnorm(-2) = .95

e. P(mu-3sigma<X<mu+3sigma) =pnorm(3)-pnorm(-3) = .997

P(X=c) = .80

R code

m<-155

s<-27

This is the 80th percentile at 177.68 mg/dl

20th percentile is c

P(X=c) = .20

R code

m<-155

s<-27

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