The authors of the article “Dynamics of Canopy Structure and Light Interception in Pinus elliotti, North Florida” (Ecol. Monogr. 1991: 33–51) planned an experiment to determine the effect of fertilizer on a measure of leaf area. A number of plots were available for the study, and half were selected at random to be fertilized. To ensure that the plots to receive the fertilizer and the control plots were similar, before beginning the experiment tree density (the number of trees per hectare) was recorded for eight plots to be fertilized and eight control plots, resulting in the given data. Minitab output follows.

a. Construct a comparative boxplot and comment on any interesting features.
b. Would you conclude that there is a significant difference in the mean tree density for fertilizer and control plots? Use α = .05.

c. Interpret the given confidence interval.

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Fertilizer 1024 1216 1312 1280 1216 1312 992 1120 plots Control 1104 1072 1088 1328 1376 1280 1120 1200 plots Two sample T for fertilize vs. control Fertilize Control N 8 8 Mean 1184 1196 Std. Dev. SE Mean 44 42 126 118 95% CI for mu fertilize-mu control: (-144, 120)