Difference between factorial design and custom design

[#1]

Hello:

I am just trying to understand the reason behind different experiments in factorial and custom design.

I have three factors all of them are continuous. Two factors have three levels while one factor has two level.

I initially did a normal full factorial design having 18 experiments with no replicates.

Below is the experiment set-up that I got

Below plot shows the wing_length vs base_length experiments and we can see points at all the levels.

Than I created the design using custom design and entered the exact factor levels with no factor constraints.

Below is the set up and design table that I got. I have also plotted the wing_length vs base_length experiments. There are no midpoints (4.5) considered in the design experiments. Is there any specific reason for that?

Any help is highly appreciated.

Best Regards,

Varun Katiyar

[#2 · Accepted solution]

In the custom design, you did not specify any quadratic effects, so you are just getting the linear effects you asked for (necessary).

[#3]

Than you statman that worked.