A soil scientist is studying the potassium content of three major soil types in Texas. For each of the three soil types, the scientist randomly selects five sites in which this soil type is the dominant soil type within the site. Within each site, five soil samples are randomly selected and the potassium content is determined. The soil scientist is interested in the level of difference in the average potassium content across the three soil types, and the degree of variability in potassium content within sites.
a. Identify each of the factors as fixed or random; justify your answer.
b. State whether the factors are nested or crossed; provide reasons for your answers.
c. Provide an AOV table that includes source of variation, df, and expected mean squares.