Statistics for Six Sigma Green Belts with Minitab and JMP

ANOVA Assumptions

To use the one-way ANOVA F test, you must make three assumptions about the underlying populations:

1. Randomness and independence.

2. Normality.

3. All populations have the same variance.

The first assumption, randomness and independence, always must be met because the validity of any experiment depends on random sampling and/or the randomization process. To avoid biases in the outcomes, you need to either select random samples from the populations or randomly assign the items or individuals to the levels of the factor of interest (i.e., the CTP categories, called treatment groups or levels of X). Departures from this assumption can seriously affect inferences from the ANOVA. These problems are discussed more thoroughly in Reference ...