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Table 3 Orthogonal coding of dummy variables for nominal categorical factor levels using a single variable for 2 levels, two variables for 3 to 4 levels and three variables for 5 to 8 levels

From: Balance algorithm for cluster randomized trials

Number of levels

Level

Var1

Var2

Var3

2

1

-1

N/A

N/A

 

2

1

  

3

1

-1

-1

N/A

 

2

1

-1

 
 

3

-1

1

 

4

1

-1

-1

N/A

 

2

1

-1

 
 

3

-1

1

 
 

4

1

1

 

5

1

-1

-1

-1

 

2

1

-1

-1

 

3

-1

1

-1

 

4

-1

-1

1

 

5

1

1

1

6

1

1

-1

-1

 

2

-1

1

-1

 

3

-1

-1

1

 

4

-1

1

1

 

5

1

-1

1

 

6

1

1

-1

7

1

-1

-1

-1

 

2

1

-1

-1

 

3

-1

1

-1

 

4

-1

-1

1

 

5

-1

1

1

 

6

1

-1

1

 

7

1

1

-1

8

1

-1

-1

-1

 

2

-1

-1

1

 

3

-1

1

-1

 

4

-1

1

1

 

5

1

-1

-1

 

6

1

1

-1

 

7

1

-1

1

 

8

1

1

1

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BMC Medical Research Methodology

ISSN: 1471-2288

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