Programming the statistical procedures from SAS

2 x 2 factorial with a control

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2 x 2 factorial with a control

Design: 2 x 2 factorial plus a control.

Fed all hogs a basal diet and then fed 1 of 4 treatment supplements. For the control group, we just fed additional basal diet vs. any form of "supplement."

factor 1: type of feed ingredient (ROUGH), which is either cottonseed hulls or juniper

factor 2: percentage of that ingredient in the diet (CONC), which is 20 or 40% of diet

 

I am interested of course, in the interaction, but am also interested in seeing if any of the 4 trt groups are different than the control group.

 

Questions

do I analyze the factorial 1st, (using "ROUGH" and "CONC" and ROUGH*CONC in my model) and then re-analyze to see if there are any differences between trt & CNTL?

 

Or, do I just do an "all-pairwise comparison" and use "TRT" in my model statement (not "ROUGH and CONC")? Or various contrast statements?

 

OR?

 

Ex of data

ID     TRT ROUGH CONC DATE DAY Period BWkg
5     20JUN JUN 20 6-1 19 1 19.5
8     20JUN JUN 20 6-1 19 1 12.7
9     20JUN JUN 20 6-1 19 1 25.0
16     20JUN JUN 20 6-1 19 1 29.9
30     20JUN JUN 20 6-1 19 1 17.2
5     20JUN JUN 20 6-10 28 2 22.2
8     20JUN JUN 20 6-10 28 2 14.1
9     20JUN JUN 20 6-10 28 2 25.9
16     20JUN JUN 20 6-10 28 2 33.6
30     20JUN JUN 20 6-10 28 2 19.1
5     20JUN JUN 20 6-17 35 3 26.8
8     20JUN JUN 20 6-17 35 3 16.8
9     20JUN JUN 20 6-17 35 3 29.5
16     20JUN JUN 20 6-17 35 3 37.7
30     20JUN JUN 20 6-17 35 3 21.8
6     20CSH CSH 20 6-1 19 1 12.7
13     20CSH CSH 20 6-1 19 1 40.8
15     20CSH CSH 20 6-1 19 1 34.9
28     20CSH CSH 20 6-1 19 1 17.7
34     20CSH CSH 20 6-1 19 1 15.4
6     20CSH CSH 20 6-10 28 2 14.5
13     20CSH CSH 20 6-10 28 2 43.1
15     20CSH CSH 20 6-10 28 2 40.8
28     20CSH CSH 20 6-10 28 2 20.4
34     20CSH CSH 20 6-10 28 2 18.6
6     20CSH CSH 20 6-17 35 3 15.0
13     20CSH CSH 20 6-17 35 3 46.7
15     20CSH CSH 20 6-17 35 3 42.2
28     20CSH CSH 20 6-17 35 3 22.7
34     20CSH CSH 20 6-17 35 3 20.9
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