The Randomized Complete Block design (RCB)
The RCB is the standard design for agricultural experiments. The field or orchard is divided into units to account for any variation in the field. Treatments are then assigned at random to the subjects in the blocks-once in each block.
- Treatments are assigned at random within blocks of adjacent subjects, each treatment once per
- The number of blocks is the number of replications.
- Any treatment can be adjacent to any other treatment, but not to the same treatment within the block.
- Used to control variation in an experiment by accounting for spatial effects.
Different colors represent different treatments; each horizontal row represents a block. There are 4 blocks (I-IV) and 4 treatments (A-D) in this example.
Block I A B C D
Block II D A B C
Block III B D C A
Block IV C A B D
ANOVA table format:
|awhere t=number of treatments and b=number of blocks or replications.|
Sample ANOVA table:
|aF test with 3,9 degrees of freedom at P=0.05 is 3.86|
Sample SAS GLM statements:
CLASS BLOCKS TREATS;
MODEL WHATEVER = BLOCKS TREATS;
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Friday, August 25, 2000