Please solve all three multiple choice questions.

1. A linear regression of age (x) on blood lead levels (y) is performed in a sample of men who have worked in factories that manufacture car batteries. The residual plots suggest there is still a pattern remaining, and you decide to add a cubic term for age into the model. Which of the following models is now most appropriate?

a. Blood lead levels =+²₁(age) +,~iid N(0,²)

b. Blood lead levels =+₁(age³) +²,~ iid N(0,²)

c. Blood lead levels =+₁(age) +₂(age²) +,~iid N(0,²)

d. Blood lead levels =+₁(age) +₂(age²) +₁(age³) +,~iid N(0,²)

2. A study has been conducted to analyze the sensitivity and specificity of a screening test. If the area under the ROC curve is 1:

a.The screening test is very helpful.

b.The screening test is not helpful.

c.The screening test is somewhat helpful.

d.Helpfulness cannot be determined from the information given.

3. An investigator is predicting systolic blood pressure by minutes of moderate exercise. If the regression line is Y = 130 - 0.5* X. What will be the difference of systolic blood pressure for a person that did 30 minutes of moderate exercise and a person that did 40 minutes of moderate exercise?

a.115

b.10

c.120

d.5