Sports Medicine Example

1
Sports Medicine Example
2
Background

• Does Sports Med Fellowship have an impact?

• Study Design
• Compare people with fellowship to those without
  on ABFM exams
• Choose target content items as DV, other items as
  covariate.

3
A Word of Warning

• ANCOVA
• Assign to treatment
• Measured category
• Covariate can either increase power of test for
  categorical variable or destroy it

4
Data Collection

• Family Med exams
• Item types
• Judges
• Item selection
• Item sums
• Nmsk
• FM
• Fellowship

5
Distribution of Criterion

•  
• Histogram
  Boxplot
• 13.25
  65
• .
  
• .
  156
• .
  
• .
  400
• .
  
• .
  941
• .
  
• .
  1764 -----
• .
  
• .
  2334 -----
• .
  
• 7.25
  2240
• .
  
• .
  1494 -----
• .
  
• .
  786

M7.66, SD1.83
6
Distribution of Covariate
Histogram
Boxplot
227.5
2 0 .
.
19
.
139
.
441
202.5
909
.
1461 -----
.
1669
.
1649 ----
.
1494
177.5
1140 -----
.
778
.
448 .
220
.
126
152.5
50 0
.
28 0 .
16
0 .
2
0 .
4 0
127.5
1 .
1
.
3
.
4
. 102.5
2
------------------------------
--------- may represent up to
35 counts
M186.63, SD12.39
7
Distribution of Categorical Variable
The FREQ Procedure  
Cumulative
Cumulative fellow Frequency
Percent Frequency Percent
ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒ
ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒ 0
8896 83.88 8896 83.88
1 1710 16.12
10606 100.00
8
Correlations
Pearson Correlation
Coefficients, N 10606
Prob gt r under H0 Rho0  
nmsk fellow
fm   nmsk
1.00000 0.07397 0.30741
lt.0001
lt.0001   fellow
0.07397 1.00000 0.04147
lt.0001
lt.0001   fm
0.30741 0.04147 1.00000
lt.0001 lt.0001
9
ANCOVA Model 1

• Dependent Variable nmsk
•  
• 
  Sum of
• Source DF
  Squares Mean Square F Value Pr gt F
•  
• Model 3
  3479.97692 1159.99231 385.81 lt.0001
•  
• Error 10602
  31876.67525 3.00667
•  
• Corrected Total 10605
  35356.65218
•  
•  
• R-Square Coeff Var
  Root MSE nmsk Mean
•  
• 0.098425 22.64258
  1.733974 7.658024
•  
• 
  Standard
• Parameter Estimate
  Error t Value Pr gt t
•  

10
ANCOVA Model 2

• Dependent Variable nmsk
•  
• 
  Sum of
• Source DF
  Squares Mean Square F Value Pr gt F
•  
• Model 2
  3473.99160 1736.99580 577.66 lt.0001
•  
• Error 10603
  31882.66057 3.00695
•  
• Corrected Total 10605
  35356.65218
•  
•  
• R-Square Coeff Var
  Root MSE nmsk Mean
•  
• 0.098256 22.64364
  1.734055 7.658024
•  
•  
•  
• 
  Standard

11
Graph of Result