Question: A researcher wants to explore the relationship between age and levels of steroid in females aged 8 to 25 years. The residual plots and fitted line plots for two models are shown below based on age only, or age, age ² , and age ³ .

a.) Based on the graphs above, which model do you prefer? Explain.

The output for the cubic model is shown below. All other parts refer to this output.

b.) Write the prediction equation for estimating the average steroid level.

c.) If Susan's steroid level is 25.148 and she is 20 years old, what is Susan's residual value?

d.) What proportion of the variation in Steroid levels is explained by AGE, AGE2 and AGE3?

e.) Is there evidence to suggest that AGE3 is not needed? Explain.

f.) What is the value of the residual for the point denoted by the arrow on the previous page?

g.) Estimate the standard deviation about the regression for the cubic model

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Solution: The downloadable solution consists of 3 pages
Deliverable: Word Document