7.5: Try It!

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Exercise \(\PageIndex{1}\)

A poultry experiment was run to investigate the effect of diet and antibiotics on egg production. They evaluated 2 diets of interest and 2 specific antibiotics that are on the market. The feed and antibiotic were combined and used to fill the feeding trays in barns. They chose 3 poultry farms at random and randomly assigned the combinations of diet and antibiotic to 4 barns within each farm. Total egg production by the chickens was recorded after 4 weeks.

What is the experimental design (hint: think about the randomization process)?
Identify which factors are fixed and which are random.

Show Solution

a) RCBD

b) Fixed factors: Diet and Antibiotic; Random factor: Farms

Exercise \(\PageIndex{2}\)

A commercial farmer is studying the corn yield of two fertilizer types at 2 different temperature levels. He strips his cornfield into 20 strips. Each fertilizer type and temperature level combination is then assigned to 5 of the randomly chosen strips.

What is the Treatment design?
What is the Randomization design?

Show Solution

a) \(2 \times 2\) factorial with fertilizer types and temperature levels, each having 2 levels

b) CRD with 5 replicates

Exercise \(\PageIndex{3}\)

An investigator wants to run an experiment in a Latin square design evaluating 5 levels of a treatment (labeled A, B, C, D, and E) and included the layout in a research proposal that you are reviewing. Identify any problems you see and suggest how to revise the design.

A	B	C	D	E
B	C	D	B	A
C	D	E	A	B
D	E	A	B	C
E	A	B	C	D

Show Solution: Column 4, row 2, B should be E to satisfy the property that each treatment occurs only once in each row and once in each column. In addition, the rows and columns need to be independently randomized to produce the actual layout of the Latin square for the experimental plan.