Question: Scientists debate the effects of increased carbon dioxide in the atmosphere, largely the result of burning fossil fuels. But atmospheric carbon dioxide levels have varied widely in the past in response to swings in the earth's general metabolism. If scientists knew what past levels were, they might be better able to predict what current levels portend. Scientists in the Netherlands and in Florida have proposed a method of determining carbon dioxide levels in past atmospheres by examining fossilized plants. They have discovered that leaves of certain plants respond to different levels of carbon dioxide by developing different numbers of stomata (pores) on the undersides of their leaves. Since fossilized leaves dating back to 10 million years ago are available, a technique based on stomata counts may provide strong insights. (Data from R. Monastersky, "The Leaf Annals," Science News 144 (August 28, 1993): 140-41.) How could one design a study with live plants in a laboratory setting that would calibrate stomata counts in such a way that carbon dioxide levels could be estimated? Discuss confounding variables, blocking, etc. Describe the analysis. Do not attempt a sample size calculation