In: Statistics and Probability
(1 point) 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
2.84 | 2.69 | 2.9 | 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
3.16 | 3.38 | 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 compressed soil relative to intermediate soil. Compute degrees of freedom using the conservative method.
Interval: ________ to -.2519
x1 = | 2.906 | x2 = | 3.337 |
s1 = | 0.139 | s2 = | 0.318 |
n1 = | 20 | n2 = | 20 |
Point estimate =x1-x2= | -0.431 |
degree of freedom v ='min(n1,n2)-1= | 19 |
std error =√(S21/n1+S22/n2)= | 0.0776 |
Point estimate of differnce =x1-x2 = | -0.431 | ||
for 96 % CI & 19 df value of t= | 2.205 | ||
margin of error E=t*std error = | 0.171 | ||
lower bound=mean difference-E = | -0.6022 | ||
Upper bound=mean differnce +E = | -0.2598 | ||
from above 96% confidence interval for population mean =(-0.6022 , -0.2598) |