5. Mercury Concentration in Dolphins The mercury concentrations in striped dolphins were measured as part of a marine pollution study. This concentration is expected to differ in males and females because the mercury in a female is apparently transferred to her offspring during gestation and nursing. The study involved 28 males between the ages of .21 and 39.5 years, and 17 females between the ages of .80 and 34.5 years.

For the data in the table,

a. Write a second-order model relating y to 1 x and 2 x .
Allow for curvature in the relationship between age and mercury concentration, and allow for an interaction between gender and age.
Use a computer software package to perform the multiple regression analysis. Refer to the printout to answer these questions.

b. Comment on the fit of the model, using relevant statistics from the printout.

c. What is the prediction equation for predicting the mercury concentration in a female dolphin as a function of its age?

d. What is the prediction equation for predicting the mercury concentration in a male dolphin as a function of its age?

e. Does the quadratic term in the prediction equation for females contribute significantly to the prediction of the mercury concentration in a female dolphin?

f. Are there any other important conclusions that you feel were not considered regarding the fitted prediction equation?

Transcribed Image Text:

x, Age of the dolphin (in years) = Jo if female 1 if male y = Mercury concentration (in micrograms/gram) in the liver y x X y x X 1.70 21 1 481.00 22.50 1 1.72 33 1 485.00 24.50 1 8.80 2.00 1 221.00 24.50 1 5.90 2.20 1 406.00 25.50 1 101.00 8.50 252.00 26.50 1 85.40 11.50 1 329.00 26.50 1 118.00 11.50 1 316.00 26.50 1 183.00 13.50 1 445.00 26.50 1 168.00 16.50 1 278.00 27.50 1 218.00 16.50 1 286.00 28.50 1 180.00 17.50 1 315.00 29.50 1 264.00 20.50 1 y y X 241.00 31.50 1 142.00 17.50 0 397.00 31.50 1 180.00 17.50 0 209.00 36.50 1 174.00 18.50 0 314.00 37.50 1 247.00 19.50 0 318.00 39.50 1 223.00 21.50 2.50 .80 9.35 1.58 0 4.01 1.75 0 29.80 5.50 45.30 7.50 101.00 8.05 135.00 11.50 0 ooooooo 0 167.00 21.50 157.00 25.50 0 177.00 25.50 475.00 32.50 0 342.00 34.50 oooooo 0 0 0 0 0 0