1. What is the value for z (0.67 ) [ area to the right of 0.67] ? A +0.67 B -0.4

Question

1. What is the value for z(0.67) [ area to the right of 0.67] ?

A +0.67

B   -0.44

C. 0.2486

D. - 0.17

2. High blood cholesterol increases the risk of atherosclerosis, the thickening of the arteries that can reduce blood flow to the heart, brain, kidneys, etc. This increases the risk of heart attack, stroke, kidney failure, etc. The cholesterol level for adult males of a specific racial group is approximately normally distributed with a mean of 4.8 mmol/L and a standard deviation of 0.6 mmol/L.

A person has high risk if his cholesterol level is more than 2 standard deviations above the mean, i.e., greater than 6.0 mmol/L. What proportion of the population has high risk?

3. A large brass company had a labor contract that required any employee layoffs to be based on the employee’s years of service with the company (seniority). A cutoff value is determined, and any employee whose seniority is less than the value is laid off. At one plant, seniority is normally distributed with mean 15 years and standard deviation 5 years. If 18% are to be laid off, what is the cutoff value?

4. A mathematics instructor studies the lengths of time required for students to complete the final examination. She found that the mean time was 90 minutes and the standard deviation 10 minutes. If the lengths of time are normally distributed.

a. 95% of all lengths of time will fall between what two times?

b. 99.7% of the students will complete the final examination between what two times?

" Please explain how would you get the answers"

Explanation / Answer

Ans:

1)Area to the right of z=0.67

P(Z>=z)=0.67

P(Z<=z)=1-0.67=0.33

z=normsinv(0.33)=-0.44

2)

z(6)=(6-4.8)/0.6=2

P(z>2)=0.02275

3)

P(Z<=z)=0.18

z=-0.915

cut off value=x=15-0.915*5=10.425 years

4)mean=90

standard deviation=10

a)According to empirical rule,95% of the data fall within 2 standard deviations.

so,

lower limit=90-2*10=70

upper limit=90+2*10=110

b)According to empirical rule,99.7% of the data fall within 3 standard deviations.

so,

lower limit=90-3*!0=60

upper limit=90+3*10=120

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.