Unequal size of blocks

Question

Hi all,

I would like to ask about the unequal size of blocks in a 2^3 Custom Design.

You know that it can be conducted in Custom Design with checking the combo box with a certain number generating separated blocks. In case of that we have 8/3 like below, JMP shows me unblanced blocking arrays.

I wonder if it is okay with it. Does anything exist disadvantages or issues with unequal size of blocks?

I am looking forward to checking answers with powerful evidences as soon as possible. Thanks

cwillden · Accepted Answer

It's not ideal, but is completely ok.  The beauty of optimal design is that you don't have to strictly enforce all these design properties like full orthogonality, balance, etc.  You can compromise a bit on those things in order to find a design that fits your situation rather than try to force fit your situation to a design.  In reality, the cost of that compromise is usually much smaller than you might anticipate.  Look at the design diagnostics and verify that it meets your needs.  You can run an analysis with simulated data or use Compare Designs with block sizes that would allow for balance (sizes 2 and 4) versus block size = 3 to give yourself more confidence about it.