4) The Skyros wall lizard (Podacris gaigeae) is native to Greece and a number of small islands off the Greek coast. Rese

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4 The Skyros Wall Lizard Podacris Gaigeae Is Native To Greece And A Number Of Small Islands Off The Greek Coast Rese 1 (163.31 KiB) Viewed 32 times

4) The Skyros wall lizard (Podacris gaigeae) is native to Greece and a number of small islands off the Greek coast. Researchers established that hard-shelled invertebrates on the island are disproportionately common relative to the mainland, and they were interested in whether the island lizards had evolved to cope with these harder prey. They collected lizards from both mainland and island populations and measured their bite force by enticing the lizards to bite a small air-filled plastic tube. The bite changed the air pressure in the tube, and this was recorded by an electronic transducer. a) The Excel file entitled “lizard” contains all of the data from this experiment: environment, headwdth (mm), BiteForce (unitless, but higher number equal higher force), and the logio of bite force, LBiteForce. Use the aoy function in R to test the null hypothesis that there is no difference in mean log10 bite force between mainland and island lizard populations. State your conclusions (5 points). b) Bite force is, in part, a function of the size of the lizard - and in particular the size of the muscles in the head. The researchers measured the head width on each lizard in the study. Use head width as a covariate and reanalyze the data with the aoy function in R to test the null hypothesis that there is no difference in bite force between mainland and island lizard populations. Be sure to test the homogeneity of slopes assumption and explain what this assumption means. Report your conclusions. Why are simple arithmetic means inappropriate to report after this analysis? What are the appropriate means? (12 points) c) Which analysis (part la or 1b) is more powerful? Explain in technical terms how the power changes. (5 points)