Mussel larvae are in great abundance in the drift material that washes up on Ninety Mile Beach in New Zealand. These larvae tend to settle on algae. Environmentalists at the University of Auckland investigated the impact of algae type on the abundance of mussel larvae in drift material. (Malacologia, Feb. 8, 2002.) Drift material from three different wash-up events on Ninety Mile Beach were collected; for each wash-up, the algae was separated into four strata—coarse-branching, medium-branching, fine-branching, and hydroid algae. Two samples were randomly selected for each of the 3 × 4 = 12 event/strata combinations, and the mussel density (percent per square centimeter) was measured for each. The data were analyzed as a complete 3 × 4 factorial design. The ANOVA summary table is shown here.

a. Identify the factors (and levels) in this experiment.

b. How many treatments are included in the experiment?

c. How many replications are included in the experiment?

d. What is the total sample size for the experiment?

e. What is the response variable measured?

f. Which ANOVA F test should be conducted first? Conduct this test (at α = .05) and interpret the results.

g. If appropriate, conduct the F tests (at α = .05) for the main effects. Interpret the results.

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source df p-Value Event 35 >.05 Strata 3 217.33 >.05 Interaction 6. 1.91 >.05 Error 12 Total 23 2.