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3.1 Factorial designs with two treatment factors 333.1 Factorial designs with two treatment factorsOne of the great advantages of analysis ofvariance is that it allows you to examineseveral different treatment factors at once.Suppose that we have an experiment oncanola (oil-seed rape) with two treatmentfactors, N (nitrogen) and S (sulphur), in arandomized-block design (factor block)with three blocks and twelve plots (factorplot) per block. The data are available inGenStat spreadsheet file Canola.gsh(Figure 3.1).This is a two-way analysis ofvariance in randomized blocks,which can be analysed by the Oneandtwo-way Analysis of Variancemenu. Figure 3.2 shows the menuwith all the relevant fields filled in,and the resulting output is shownbelow.Figure 3.1Figure 3.2Analysis of varianceVariate: yieldSource of variation d.f. s.s. m.s. v.r. F pr.block stratum 2 0.30850 0.15425 3.44block.*Units* stratumN 2 4.59223 2.29611 51.22