Blocking

[Benjamin]

Hi!

When using an efficient design, with only signs for parameter (i.e. [0.000001])

Is it possible (necessary) to block? Want to maximum give 4 choice sets to each respondent, but need at least 13 choice sets. Block in 4 from 16 ?
Or is blocking only from orthogonal?

[Michiel Bliemer]

True blocking is only possible in orthogonal designs, HOWEVER, we have implemented a heuristic in Ngene that lets you blick any design. Ngene aims to minimise correlations between attribute levels within a block, which results in blocks that have a high degree of attribute level balance. So you can use blocking also with an efficient design in Ngene, and indeed block a design of 16 into 4.

[Benjamin]

Thanks!

When only using +/- for priors, what would be best in Ngene, orthogonal 16/4 or efficient design 16/4, or both (i.e. orth=seq + eff=(mnl,d)) ?

[Michiel Bliemer]

Efficient, since this allows Ngene to remove dominant alternatives by setting ;alts = alt1*, alt2*. If you do not want to check for dominant alternatives then both orth = seq or eff is good in case your priors are (near) zero.