Question

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 two 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	2.66	2.95	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

3.11	3.32	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 99.5% confidence interval for the decrease in penetrability of compressed soil relative to intermediate soil. Compute degrees of freedom using the conservative method.

Interval: to

please show your work and what function to use on the calculator. thank you !

Answer 1

Compressed Soil

box plot shows that there are no outliers.

Intermediate Soil

Box plot shows that there is an outlier. (outlier is 4.26)

calculate mean and standard deviation without outlier

for sample 1(compressed soil)

for sample 2 (intermediate soil)

confidence interval calculations

So required confidence interval is (-0.56,-0.187).