The concentration of carbon dioxide (CO 2 ) in the atmosphere is increasing rapi

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.

The concentration of carbon dioxide (CO in the atmosphere fossil fuels. Beca CO, to fuel photosynthe sing rapidly due to They selected tn coch three parts of Pine forest and randomly chese of coch point: extra co2. The response variable 10,654 7.225 5.164. State the null and alternative hypotheen (Whem p H.: preconceived ides what extrs coa wil de te the growth rate rchers have that Co. will growth rate. The researchers have reason to believe that co, wal increase prowth rete. (b) Camy -ut test and report your cen-usion in simple language. (U 0.05. u r 2 decimal Place) E- 1737 o There is evidence or a increase in growth rates due to extra co rates due to extra cos The estig tors used the test rried out. Any of the proced mples this size is risky. Why O The procedure should only be used for Isrge samples. The t Pr endure should only be used for emal samples from Normal Population CO, may trees and other plants to grow tester An elaborate apparatus allows d-ring growing rchers to pipe extra co. to 30-meter circle of forest. this in percent incre se per year's

Explanation / Answer

treated

control

Diff(D)

10.684

9.784

0.9

8.164

7.225

0.939

6.776

5.756

1.02

Average of D= D = (0.9+0.939+1.02)/3 = 0.953

Standard deviation of D = (D - D)2 / n-1 = 0.061213

H0 = µ = 0

H1 = µ > 0

t = n * D / sD = 3 * 0.953 / 0.061213 = 26.97

t critical value from the table for = 0.05 for 2 df = 2.920

Since the calculated value of t = 26.97 > t critical value = 2.920, we reject the null hypothesis and conclude that there is evidence of a increase in growth rate due to CO2.

treated

control

Diff(D)

10.684

9.784

0.9

8.164

7.225

0.939

6.776

5.756

1.02

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