Logging in the rain forest. How does logging in a tropical rain forest affect the forest in later years? Researchers compared forest plots in Borneo that had never been logged (Group 1) with similar plots nearby that had been logged 1 year earlier

(Group 2) and 8 years earlier (Group 3). Although the study was not an experiment, the authors explain why we can consider the plots to be randomly selected.

The data appear in Table 24.2 (page 640). The variable Trees is the count of trees in a plot; Species is the count of tree species in a plot. The variable Richness is Species/Trees, the number of species divided by the number of individual trees.4

(a) Make side-by-side stemplots of Trees for the three groups. Use stems 0, 1, 2, and 3 and split the stems (see page 21). What effects of logging are visible?

(b) Figure 24.4 (page 640) shows Excel ANOVA output for Trees. What do the group means show about the effects of logging?

(c) What are the values of the ANOVA F statistic and its P-value? What hypotheses does F test? What conclusions about the effects of logging on number of trees do the data lead to?