An important issue in conservation biology is how dispersal among populations influences the persistence of species in a fragmented landscape. Molofsky and Ferdy (2005) measured this in the annual plant Cardamine pensylvanica, a weed that produces explosively dispersed seeds. Four treatments were used to manipulate seed dispersal by changing the distance among experimental plant populations. These treatments were adjacent (continuous treatment), separated by 23.2 cm (medium), separated by 49.5 cm (long), or separated by partitions that blocked all seed dispersal among populations (isolated). Treatments were randomly assigned to plant populations. The data below are the number of generations that the populations persisted in four replicates of each treatment.

a. What is the explanatory variable in this analysis? What is the response variable?

b. Is this an experimental study or an observational study? Explain.

c. What are the null and alternative hypotheses being tested?

d. Fill in the rest of the table.

e. What is the sampling distribution of the F-statistic under the null hypothesis?

f. What does P measure?

g. In words, explain what each “sum of squares” measures.

h. If you wanted to determine the fraction of the variation in generations persisted that is “explained” by treatment, what quantity would you use?

i. Calculate the quantity identified in part (f).

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Treatment Isolated Isolated MediumMedium LongLong ContinuousContinuous Generations persisted 13.8.8.8. 13, 8, 8, 8, 14,12,16,16, 14, 12, 16, 16, 13,9,10,11, 13, 9, 10, 11, 9,13,13.16, 9, 13, 13, 16,