The concentration of carbon dioxide (CO 2 ) in the atmosphere is increasing rapi
ID: 3177077 • Letter: T
Question
The concentration of carbon dioxide (CO2) in the atmosphere is increasing rapidly due to our use of fossil fuels. Because green plants use CO2 to fuel photosynthesis, more CO2 may cause trees to grow faster. An elaborate apparatus allows researchers to pipe extra CO2 to a 30-meter circle of forest. We want to compare the growth in base area of trees in treated and untreated areas to see if extra CO2 does in fact increase growth. We can afford to treat three circular areas.
Step 1:
Describe the design of a completely randomized experiment using six well-separated 30-meter circular areas in a pine forest.
Step 2:
Areas within the forest may differ in soil fertility. Describe a matched pairs design using three pairs of circles that will reduce the extra variation due to different fertility.
Explanation / Answer
Solution:-
step 1: option C. Sketch 6 well-separated 30-meter circular areas in the pine forest. Randomly choose 3 of them and treat them with extra CO2. Compare the growth of trees in the two groups.
step 2: option D. Sketch 3 pairs of well-separated 30-meter circular areas in the pine forest. Trees in each pair must be similar in their soil fertility. Randomly choose one area from each pair and treat it with extra CO2. Compare the growth of the treated trees with the growth of the untreated ones.
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