Assignment:
A soil scientist conducted an experiment to evaluate the effects of soil compaction and soil moisture on the activity of soil microbes. Reduced levels of microbe activity will occur in poorly aerated soils. The aeration levels can be restricted in highly saturated or compacted soils. Treated soil samples were placed in airtight containers and incubated under conditions conductive to microbial activity. The microbe activity in each soil sample was measured as the percent increase in CO2 produced above atmospheric levels.
The treatment design was a 3x3 factorialwith three levels of soil compaction (bulk density = mg soil/cubic meter) and three levels of soil moisture (kg water/kg soil). There were two replicate soil container unitsprepared for each treatment.
The CO2 evolution/kg soil/day was recorded onthree successive days. The data for each soil container unit are shown in the table (attached). Write alinear modelfor a split-plot analysis of variance,identify the terms, and indicate theassumptionsnecessary for the analysis with this model.
a. Conduct a split-plot analysis for the data, test the necessary hypotheses, and compute treatment means and their standard errors. What are your conclusions?
b. Obtain the residual plots from the split-plot analysis, and interpret them.
c. Compute the sum of squares partitions for the linear, quadratic, and cubic contrasts on time and their interactions with density and moisture treatments; test the null hypotheses, and interpret the results.