Partitioning the Sums of Squares (6 of 7)

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The ANOVA Summary Table
It is convenient to view the results of an analysis of variance in a summary table. The summary table for the example data is shown below.

Source    df    Ssq     Ms     F     p
 Groups   2    8.000  4.000  3.60 0.071
 Error    9   10.000  1.111
Total    11   18.000  1.636

The first column contains the source of variation (or source for short). There are two sources of variation: differences among treatment groups and error. The second column contains the degrees of freedom (df). The df for groups is always equal to the number of groups minus one. The df for error is equal to the number of subjects minus the number of groups. The formulas for the degrees of freedom are shown below:

df_groups = a - 1 = 3 - 1 = 2
df_error = N - a = 12 - 3 = 9
df_total = N - 1 = 12 - 1 = 11

a is the number groups
N is the total number of subjects.
df_total = df_groups + df_error