8.7 It is conjectured that when fields are overgrazed by cattle there will be a substantial reduc- tion in the available grass during the subsequent grazing season due to the compaction of the soil. A horticulturist at the state agricultural experiment station designs a study to evaluate the conjec- ture. Twenty-one plots of land of nearly the same soil texture and suitable for grazing are selected for the study. Three grazing regimens selected for evaluation are randomly assigned to 7 plots each. After the 21 plots are subjected to the grazing regimens for four months, the researcher randomly selects 10 soil cores from each plot and measures the bulk density (g/cm3) in each soil core. The mean soil density of the 10 cores from each plot is given in the following table. Grazing Regimen Soil Denisty (g/cm3) Continuous grazing 2.05 3.05 3.12 1.59 3.83 1.53 1.44 Three-week grazing, one-week no grazing 1.20 1.48 3.54 1.03 1.45 1.40 2.68 Two-week grazing, two-week grazing 1.23 1.66 1.70 1.29 1.26 1.05 2.35 a. Do the grazing regimens appear to yield different degrees of effect on the amount of compacting in the soil? Justify your answer using an a 5 .05 test. b. Provide the level of significance of your test. c. Do any of the conditions necessary for conducting your test appear to be violated? Justify your answer.
8.7
It is conjectured that when fields are overgrazed by cattle there will be a substantial reduc- tion in the available grass during the subsequent grazing season due to the compaction of the soil. A horticulturist at the state agricultural experiment station designs a study to evaluate the conjec- ture. Twenty-one plots of land of nearly the same soil texture and suitable for grazing are selected for the study. Three grazing regimens selected for evaluation are randomly assigned to 7 plots each. After the 21 plots are subjected to the grazing regimens for four months, the researcher randomly selects 10 soil cores from each plot and measures the bulk density (g/cm3) in each soil core. The mean soil density of the 10 cores from each plot is given in the following table.
Grazing Regimen Soil Denisty (g/cm3)
| Continuous grazing | 2.05 | 3.05 | 3.12 | 1.59 | 3.83 | 1.53 | 1.44 |
| Three-week grazing, one-week no grazing | 1.20 | 1.48 | 3.54 | 1.03 | 1.45 | 1.40 | 2.68 |
| Two-week grazing, two-week grazing | 1.23 | 1.66 | 1.70 | 1.29 | 1.26 | 1.05 | 2.35 |
a. Do the grazing regimens appear to yield different degrees of effect on the amount of compacting in the soil? Justify your answer using an a 5 .05 test.
b. Provide the level of significance of your test.
c. Do any of the conditions necessary for conducting your test appear to be violated? Justify your answer.
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