Deliberative Poll proceeds as follows — Respondents are surveyed, provided ‘balanced’ briefing materials, randomly assigned to moderated small group discussions, allowed the opportunity to quiz experts or politicians in plenary sessions, and re-interviewed at the end. The “effect” is conceptualized as average Post–Pre across all participants.
The effect of the Deliberative Poll is contingent upon a particular random assignment to small groups. This isn’t an issue if small group composition doesn’t matter. If it does, then the counterfactual imagination of the ‘informed public’ is somewhat particularistic. Under those circumstances, one may want to come up with a distribution of what opinion change may look like if the assignment of participants to small groups was different. One can do this by estimating the impact of small group composition on the dependent variable of interest and then predicting the dependent variable of interest under simulated alternate assignments.