Blocked randomization

Randomly assign study participants to treatment groups in small blocks of four or six

In experimental research designs, blocked randomization is a method of randomly assigning participants to treatment groups in small "blocks" of four or six individual participants at a time.

Blocked randomization will always yield equally sized treatment groups, which increases statistical power in experimental research designs.

Because of the tedious nature of randomizing these "blocks," blocked randomization tends to be used in smaller studies with fewer study participants.

In order to conduct blocked randomization, researchers take four to six study participants out of the sampling pool and randomly assign them to treatment groups. They then take out another four to six participants and randomly assign them, and so on.

​Blocked randomization is pretty simple and very effective when conducting smaller experimental research designs. 
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