I have a list of 40 items. I order to eradicate respondent fatigue and to reduce the number of screens I am thinking of doing an express maxdiff randomly selecting 20 items (out of 40) and conducting a maxdiff out of 20 items. Teh process is detailed out in the sawtooth paper page 59 under topic "Using Maxdiff for Evaluating Very Large Sets of Items".
Here we have to create block designs by allowing the option "Individual Designs Lacking Connectivity". My questions
i) Why should we not allow connectivity between individual designs?
ii) After forming individual maxdiff designs which results to showing 12 screens per respondent with 5 items each (each respondent evaluating 20 items out of 40 here), I am exposed to the warning of versions lacking connectivity when I try to combine the designs. Is the warning ignorable?
iii) Such a design have any impact when I try to HB estimate the utilities? should I try any other method for generating utilities?