2009/07/25

Completely Randomized Design (CRD)

Completely Randomized Desing (CRD)- is a type of experimental design in which experimental subjects are randomly assigned a treatment.

Example in the study entitled "Utilization of Coir Fibers in the Production of Roofing Materials" its hypothesis would be stated this way; There is no significant difference on the breaking strength of the 5 mixtures made of same amount of coir fiber and different ratios of cement and plaster.

In the methodology possible direction of how CRD was done could be described this way:

One and one-half kilograms of coir fibers were used in this study. It was divided into 15 samples which would constitute a mass of 100 grams for each sample of coir fiber. Randomly, each of the 15 samples was mixed in the five mixtures with various ratio of cement and plaster.
To determine which of the 15 100-g coir fiber sample will be mixed with mixture 1,2,3,4, and 5 the researcher labeled the samples from letters a-o. And then, 15 small sheets of papers were also labeled the same way for drawing of lots. The first 3 picked were assigned to be mixed in mixture 1 and the same procedure were done on assigning a mixture for the remaining 100-g coir fiber samples. Determination of assigned trials for each sample was also done using CRD.

Illustration:

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