Statistics Dictionary

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Randomized Block Experiment

A randomized block experiment with independent groups is distinguished by the following attributes:

  • The design has one or more factors (i.e., one or more independent variables), each with two or more levels.
  • Treatment groups are defined by a unique combination of non-overlapping factor levels.
  • Experimental units are randomly selected from a known population.
  • Each experimental unit is assigned to one block, such that variability within blocks is less than variability between blocks.
  • The number of experimental units within each block is equal to the number of treatment groups.
  • Within each block, each experimental unit is randomly assigned to a different treatment group.
  • Each experimental unit provides one dependent variable score.

The table below shows the layout for a typical randomized block experiment.

  T1 T2 T3 T4
B1 X1,1 X1,2 X1,3 X1,4
B2 X2,1 X2,2 X2,3 X2,4
B3 X3,1 X3,2 X3,3 X3,4
B4 X4,1 X4,2 X4,3 X4,4
B5 X5,1 X5,2 X5,3 X5,4

In this experiment, there are five blocks ( Bi ) and four treatment levels ( Tj ). Dependent variable scores are represented by X i, j , where X i, j is the score for the subject in block i who received treatment j.

See also:  Randomized Block Designs | Randomized Block Experiments: Data Analysis