Plots to show the effect of individual factors

On the previous page, a 3-dimensional display was rotated to help understand the nature of the main effects and interactions. Simpler 2-dimensional diagrams plotting the mean response against the individual factors are simpler. For a factor X,

The plots are easier to understand in an example.

Wear of coated fabrics

The following diagram initially shows a model with no interactions for the fabric abrasion data.

Since the model has no interactions, simple plots of the mean abrasion loss against each factor effectively summarise the effects of changing the factors in the model.

Click the y-x rotation button. Since there is no interaction, the four coloured lines are parallel and the simpler summary diagram of mean response against percent filler averages these four lines.

Similarly click the y-z rotation button and observe that all lines are again parallel, so the simpler plot of mean response against filler type summarises the no-interaction model well.

We saw earlier that the best model had two interactions, P*F and F*S. Use the checkboxes to select this model and observe how the diagrams are modified to summarise the effects of these interactions.