Why so many sociologists don't believe the CIS survey: sample bias contaminates the polls
The experts consulted believe that the left is overrepresented because many right-wing voters refuse to participate in interviews. The public body denies it.
The latest barometer from the Centro de Investigaciones Sociológicas (CIS) has sparked controversy over its estimates of support for the PSOE, which have been overestimated on more than one occasion. The survey of 5,000 people puts the socialists well ahead of the PP, with almost a 12-point lead. This contrasts with the average of private polls. Experts say they cannot recall such a large difference between CIS data and other surveys, and point to an overrepresentation of PSOE voters in the sample.
Written by urgent.news from El Pais's report — not a translation of it. Machine-written — may contain errors; check the original before relying on it.
