An industrial psychologist working for a large corporation designs a study to evaluate t...

An industrial psychologist working for a large corporation designs a study to evaluate the effect of background music on the typing efficiency of secretaries. The psychologist selects a random sample of seven secretaries from the secretarial pool. Each subject is exposed to three types of background music: no music, classical music, and hard rock music. The subject is given a standard typing test that combines an assessment of speed with a penalty for typing errors. The particular order of the three experiments is randomized for each of the seven subjects. The results are given here with a high score indicating a superior performance. This is a special type of randomized complete block design in which a single experimental unit serves as a block and receives all treatments.

a. Write a statistical model for this experiment and estimate the parameters in your model.

b. Are there differences in the mean typing efficiency for the three types of music? Use α = .05.

c. Does the additive model for a randomized complete block design appear to be appropriate? (Hint: Plot the data as was done in Figure 15.1.)

d. Compute the relative efficiency of the randomized block design relative to a completely randomized design. Interpret this value. Were the blocks effective in reducing the variability in experimental units? Explain.

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