A randomized complete block design was employed to study the effects of three di

Question

A randomized complete block design was employed to study the effects of three diets on the reduction of total lipid (fat) level in blood plasma. Data and SAS output from fifteen male subjects who were within 20% of their ideal body weight is given in Table 2 below Explain exactly how the randomization for this design would have been done. What are the advantages and disadvantages of using a randomized block design versus a completely randomized design? Was blocking by AGE group effective? Explain your answer. Give the standard error of the difference between two means for any pair of diets.

Explanation / Answer

Answer:

a).

15 male subjects were divided in to 5 blocks according to the given age groups. Treatment is then randomly allotted to each subject within the block.

b).

In completely randomized design, all treatments are randomly allocated among all experimental subjects. This allows every experimental unit, i.e., plot, animal, soil sample, etc., to have an equal probability of receiving a treatment.

In Randomized Block Design, Experimental units are grouped into blocks according to know or suspected variation which is isolated by the blocks. Subject are sorted into homogeneous groups, called blocks and the treatments are then assigned at random within the blocks. Experimental error is usually reduced by forming blocks of similar plot.

c).

test for age group, F =0.35474/0.002415   = 146.8903

critical F(4,8) at 5% level=3.84

calculated F=146.8903 > critical F=3.84.

Test is significant. Blocking by age is effective.

d).

standard error = sqrt(0.002415) = 0.049143

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