Question

1.

(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	2.63	2.98	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

3.17	3.3	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% confidence interval for the decrease in penetrability of compressed soil relative to intermediate soil. Compute degrees of freedom using the conservative method.

2. (1 point) A market research firm supplies manufacturers with estimates of the retail sales of their products from samples of retail stores. Marketing managers are prone to look at the estimate and ignore sampling error. An SRS of  1212 stores this year shows mean sales of 7070 units of a small appliance, with a standard deviation of 8.28.2 units. During the same point in time last year, an SRS of 2929 stores had mean sales of 63.0363.03 units, with standard deviation 13.213.2 units. An increase from 63.0363.03 to 7070 is a rise of about 10%.

a) Construct a 99% confidence interval estimate of the difference μ1−μ2μ1−μ2, where μ1μ1 is the mean of this year's sales and μ2μ2 is the mean of last year's sales.

b) what is the margin of error

Answer 1