The concentration of carbon dioxide (CO2) in the atmosphere is increasing rapidly due to our use of fossil fuels. Because plants use CO2 to fuel photosynthesis, more CO2 may cause trees and other plants to grow faster. An elaborate apparatus allows researchers to pipe extra CO2 to a 30-meter circle of forest. They selected two nearby circles in each of three parts of a pine forest and randomly chose one of each pair to receive extra CO2. The response variable is the mean increase in base area for 30 to 40 trees in a circle during a growing season. We measure this in percent increase per year. Here are one year's data. Pair Control plot Treated plot Treated - Control 9.782 10.647 0.865 2 7.283 9.254 1.971 3 5.712 8.695 2.983 (a) State the null and alternative hypotheses. (Where u is the mean difference, treated minus control.) Но: и На: и ? : Explain clearly why the investigators used a one-sided alternative. The researchers have no preconceived idea what extra CO2 will do to the growth rate. The researchers have reason to believe that CO2 will decrease growth rate. The researchers have reason to believe that CO, will increase growth rate. (b) Carry out a test and report your conclusion in simple language. (Use a = 0.05. Round your answer to two decimal places.) t =

Question
The concentration of carbon dioxide (CO2) in the atmosphere is increasing rapidly due to our use of fossil fuels. Because plants use CO2 to fuel photosynthesis,
more CO2 may cause trees and other plants to grow faster. An elaborate apparatus allows researchers to pipe extra CO2 to a 30-meter circle of forest. They
selected two nearby circles in each of three parts of a pine forest and randomly chose one of each pair to receive extra CO2. The response variable is the mean
increase in base area for 30 to 40 trees in a circle during a growing season. We measure this in percent increase per year. Here are one year's data.
Pair
Control plot
Treated plot
Treated - Control
9.782
10.647
0.865
2
7.283
9.254
1.971
3
5.712
8.695
2.983
(a) State the null and alternative hypotheses. (Where u is the mean difference, treated minus control.)
Но: и
На: и
? :
Explain clearly why the investigators used a one-sided alternative.
The researchers have no preconceived idea what extra CO2 will do to the growth rate.
The researchers have reason to believe that CO2 will decrease growth rate.
The researchers have reason to believe that CO, will increase growth rate.
(b) Carry out a test and report your conclusion in simple language. (Use a = 0.05. Round your answer to two decimal places.)
t =

Image Transcription

The concentration of carbon dioxide (CO2) in the atmosphere is increasing rapidly due to our use of fossil fuels. Because plants use CO2 to fuel photosynthesis, more CO2 may cause trees and other plants to grow faster. An elaborate apparatus allows researchers to pipe extra CO2 to a 30-meter circle of forest. They selected two nearby circles in each of three parts of a pine forest and randomly chose one of each pair to receive extra CO2. The response variable is the mean increase in base area for 30 to 40 trees in a circle during a growing season. We measure this in percent increase per year. Here are one year's data. Pair Control plot Treated plot Treated - Control 9.782 10.647 0.865 2 7.283 9.254 1.971 3 5.712 8.695 2.983 (a) State the null and alternative hypotheses. (Where u is the mean difference, treated minus control.) Но: и На: и ? : Explain clearly why the investigators used a one-sided alternative. The researchers have no preconceived idea what extra CO2 will do to the growth rate. The researchers have reason to believe that CO2 will decrease growth rate. The researchers have reason to believe that CO, will increase growth rate. (b) Carry out a test and report your conclusion in simple language. (Use a = 0.05. Round your answer to two decimal places.) t =

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Hypothesis Testing

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