Two-way ANOVA

EXAMPLE:\ An agricultural scientist is interested in the corn yield when three different fertilizers are available and corn is planted in four different soil types. The questions he is interested in answering are:

1. Does fertilizer type have an effect on crop yield?
2. Does soil type have an effect on crop yield?
3. Do the two treatment factors interact? For instance, there may be no difference between fertilizer #1 and fertilizer #2 in soil type 1, but fertilizer #1 may produce a greater corn yield than fertilizer #2 in soil type 2. This is an example of interaction.

Because we are applying two treatments to our population, we will use two-way ANOVA to analyze this type of problem. We will consider two types of two-way ANOVA:

1. Two-way ANOVA without interaction (the ``additive model'').
2. Two-way ANOVA with interaction.

• The Additive Model
• Two-way ANOVA with Interaction