I'm not sure what they would use myself but based on the prequel questions they ask people plus some heuristics they can determine roughly were you sit within t

I'm not sure what they would use myself but based on the prequel questions they ask people plus some heuristics they can determine roughly were you sit within the populous on a number of aspects between age, class, income, location and political inclination etc. If a poll is biased towards political inclination they can exclude that from the selection criteria to avoid result bias.