Hi, I understand, I'm not trying to be difficult, this is just very hard to wrap my mind around and I appreciate the help! I don't think that BIBD are actually appropriate for the kind of experiment I'm thinking of. The goal is to have respondents evaluate one profile of factors at a time and to select the best and worst of the factor levels in that specific profile. Most of the literature I have seen mentions fractional factorial designs that are blocked in order to reduce respondent fatigue. I've tried to do this a few ways. First, using the %mktex macro to create a candidate set and then the %choiceff macro to search the candidate set for an efficient design, following the chair example in the Discrete Choice chapter. This seems ideal because it optimizes the variance matrix for a logit model rather than for a linear model. However, in this example %choiceff(data=design, /* candidate set of alternatives */
model=class(x1-x5 / sta), /* model with stdzd orthogonal coding */
nsets=6, /* number of choice sets */
maxiter=100, /* maximum number of designs to make */
seed=121, /* random number seed */
flags=3, /* 3 alternatives, generic candidates */
options=relative, /* display relative D-efficiency */
beta=zero) /* assumed beta vector, Ho: b=0 */ the argument "flags=3" specifies that each choice set has three alternatives, and "flags=1" is not allowed. I understand that you can block the resulting dataset using %mktblocks, however %mktblocks requires the argument nalts>1 as well. I have tried using proc optex directly, in which I first create a dataset that includes another column for the block number and use it as the input Candidate dataset, with orthogonal coding, and sepcifying a model that includes Block, e.g. proc optex data=Candidates seed=8327 coding=orth;
class F1 F2 F3 Block;
model F1 F2 F3 Block;
generate n=25 method=federov;
output out=Design number=dbest;
run; However, I'm not sure if this is doing anything different than using the ADX interface would do (which I have also tried). Finally, I'm not sure if the d-efficiency from each method of creating a design is comparable. Is there a way to use %choiceff and %mktblocks in a way to create the kind of design I described?
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