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Compare penetrability of compressed vs. intermediate soil

Farmers know that driving heavy equipment on wet soil compresses the soil and injures future crops. Here are data on the "penetrability" of the same type of soil at 2 levels of compression. Penetrability is a measure of how much resistance plant roots will meet when they try to grow through the soil.

Compressed soil:
2.86 2.68 2.92 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:
3.14 3.38 3.10 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

(a) make stemplots to investigate the shape of the distributions. The penetrabilities for intermediate soil are skewed to the right and have a high outlier. Returning to the source of the data shows that the outlying sample had unusually low soil density, so that it belongs in the "loose soil" class. We are justified in removing the outlier.

(b) We suspect that the penetrability of compressed soil is less than that of intermediate soil. Do the data (with outlier removed) support this suspicion?

Solution Summary

This solution provides a statistical significance test to compare the penetrability of compressed soil to that of intermediate soil. Stemplots to investigate the shape of compressed and intermediate soil distributions are included.