The Significance Test in ANOVA (2 of 2)


After an F is computed, the probability value can be computed from an F table. To use this table, you need to know the two degrees of freedom parameters: dfn and dfd:

dfn = a-1
dfd = N-a

where a is the number of groups and N is the total number of subjects in all groups. The parameter dfd is often called degrees of freedom error or dfe for short.

For the example data, dfn = 3-1 = 2 dfd = 12-3 = 9, MSB = 4, and MSE = 1.111.

F = MSB/MSE = 4/1.111 = 3.6.

An F table can be used to compute that the probability value for an F of 3.6 with 2 and 9 df is 0.071. Therefore the null hypothesis cannot be rejected at the 0.05 level.