Question

Completely randomized designs are suitable in the situation(s) when :

• A. all experimental units are homogeneous
• B. the units are likely to be destroyed during experimentation
• C. all experimental units are heterogeneous
• D. experimental units are in different slope

Hint:

CRD provides the maximum degrees of freedom for error, making it highly powerful, but it should ONLY be used when the experimental units are completely homogeneous.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The Completely Randomized Design (CRD) is the simplest type of experimental design.
In CRD, treatments are assigned to experimental units completely at random, with no grouping or blocking.

Step 2: Detailed Explanation:
The primary assumption for using a Completely Randomized Design (CRD) is that the experimental units are highly uniform or homogeneous.
Because there is no blocking to control for background variation, any variation among the experimental units will directly increase the experimental error.
Therefore, CRD is only suitable when:
1. The experimental material is homogeneous (e.g., laboratory experiments, greenhouse trials, or animal trials with identical breeds).
2. Environmental conditions are uniform and controlled.
If the experimental units are heterogeneous (C) or have a directional variation like a slope (D), a Randomized Block Design (RBD) or a Latin Square Design (LSD) should be used instead to control for this variation through blocking.
Thus, homogeneity of all experimental units is the essential requirement for CRD.

Step 3: Final Answer:
The correct option is (A).