The data of Exercise 12.27 were used to fit several multiple regression models; y1 = CI, y...

The data of Exercise 12.27 were used to fit several multiple regression models; y1 = CI, y2 = PCWP, x1 = age, x2 = disease duration.

I. y1 = β0 + β1x1 + β2x2 + ε

II. y1 = β0 + β1x1 + β2x2 + β3x1x2 + ε

III. y2 = β0 + β1x1 + β2x2 + ε

IV. y2 = β0 + β1x1 + β2x2 + β3x1x2 + ε

REGRESSION ANALYSIS, MODEL I

REGRESSION ANALYSIS, MODEL II

REGRESSION ANALYSIS, MODEL III

REGRESSION ANALYSIS, MODEL IV

a. Which model provides the best fit to the cardiac index data? To the pulmonary capillary wedge pressure data?

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b. Do these analyses confirm what you concluded in Exercise 12.27? Explain.

Exercise 12.27

The accompanying table gives demographic data for 12 male patients with congestive heart failure enrolled in a study of an experimental compound.

a. Summarize these data using a boxplot for each variable.

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b. Construct scatterplots to display (1) age by cardiac index (CI) and by pulmonary capillary wedge pressure (PCWP) and (2) disease duration by CI and by PCWP. Is there evidence of a correlation between age and CI or PCWP? What about correlation between duration of disease and CI or PCWP?