Completely randomized design ( CRD):

• Treatments are assigned completely at random so that each unit have same chance of receiving any one treatment.
• Done for homogenous experimental units like lab.
• Design is completely flexible.
• Suitable for situations where:

i) Experimental units are homogenous

ii) Experiments are relatively small

iii) No. of treatment is relatively small

Advantages:

• Very flexible design
• Analysis is simple compared to other designs
• Loss of information due to missing data is small.

Disadvantages:

• Not suitable if experimental units aren’t homogenous
• Not suitable for large no. of treatments