Question

The relationship between physical fitness prior to surgery of persons undergoing corrective knee surgery and the time required in physical therapy until successful rehabilitation was investigated. Subjects were 24 non-randomly selected males ranging in age from 18 to 30 years. The number of days required for successful completion of physical therapy (days), age, and prior physical fitness status (FITNESS: below average=1, average=2, above average=3) for each patient were:

ID                    FITNESS      AGE               DAYS

1                     1                      18.3                 29

2                     1                      30.0                 42

3                     1                      26.5                 38

4                     1                      28.1                 40

5                     1                      29.7                 43

6                     1                      27.8                40

7                     1                      19.8                 30

8                     1                      29.3                 42

9                     2                      20.8                 30

10                    2                      25.2                 35

11                    2                      29.2                 39

12                    2                      20.0                 28

13                    2                      21.5                 31

14                    2                      22.1                 31

15                    2                      19.7                 29

16                    2                      24.7                 35

17                    2                      20.2                 29

18                    2                      22.9                 33

19                    3                      22.7                26

20                    3                      28.7                 32

21                    3                      18.9                 21

22                    3                      18.0                 20

23                    3                      24.7                 23

24                    3                      20.0                 2

1.Use age of patients as a concomitant (confounding) variable and reanalyze the data, comparing the three fitness groups on the basis of the adjusted outcome variable. Perform an appropriate post hoc analysis. Compare the results with those reported for #1 and #2. Additionally,

• Is there a significant association between the concomitant variable and the outcome measure? If so, what does it mean?
• Has the homogeneity of regression slopes assumption been met? If so, what does it mean?
• Are there statistically significant differences among the fitness groups on the basis of age?
• Report the adjusted means for the outcome measure for each fitness level.

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Answer 1