Analysis of Two-factor Designs (1 of 5)

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A two-factor analysis of variance consists of three significance tests: a test of each of the two main effects and a test of the interaction of the variables. An analysis of variance summary table is a convenient way to display the results of the significance tests. A summary table for the hypothetical experiment described in the section on factorial designs and a graph of the means for the experiment are shown below. 
                 Sum of        Mean      
SOURCE   df      Squares      Square      F       p
     T    1    47125.3333  47125.3333  384.174   0.000
     D    2       42.6667     21.3333    0.174   0.841
    TD    2     1418.6667    709.3333    5.783   0.006
 ERROR   42     5152.0000    122.6667
 TOTAL   47    53738.6667


Sources of Variation
The summary table shows four sources of variation: (1) Task, (2) Drug dosage, (3) the Task x Drug dosage interaction, and (4) Error.
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