Farmers know that driving heavy equipment on wet soil compressesthe soil and injures future crops. Here are data on the\"penetrability\" of the same type of soil at two levels ofcompression. Penetrability is a measure of how much resistanceplant roots will meet when they try to grow through the soil.
Compressed Soil
| 2.84 | 2.63 | 2.91 | 2.82 | 2.76 | 2.81 | 2.78 | 3.08 | 2.94 | 2.86 |
| 3.08 | 2.82 | 2.78 | 2.98 | 3.00 | 2.78 | 2.96 | 2.90 | 3.18 | 3.16 |
Intermediate Soil
| 3.19 | 3.31 | 3.1 | 3.40 | 3.38 | 3.14 | 3.18 | 3.26 | 2.96 | 3.02 |
| 3.54 | 3.36 | 3.18 | 3.12 | 3.86 | 2.92 | 3.46 | 3.44 | 3.62 | 4.26 |
Use the data, omitting the high outlier, to give a 96%confidence interval for the decrease in penetrability of compressedsoil relative to intermediate soil. Compute degrees of freedomusing the conservative method.
