Article published by José Alberto León Alonso in El Día on 03/15/15.
Citizens are being subjected to a bombardment of electoral polls with disparate results regarding the elections to be held in 2015, so they end up concluding that the polls are useless, which is the same as what politicians think...when they are unfavorable to them. Given that at Corporación 5 we have been conducting market research for more than eighteen years through our subsidiary SAO, I will try to clarify doubts about the plausibility of the surveys, as well as describe our own methodology for conducting them.
To determine the reliability of a survey, it is necessary to know its working methodology, and unfortunately most surveys hide or conceal fundamental data to differentiate a technically correct survey from one that is not. Every survey, to be credible, must indicate the number of interviewees, whether the interview is in person or by telephone, direct voting intention, political sympathy, vote recall, response rate, callback strategy or substitution rule. Likewise, the sample must be well segmented by age, sex, residence, beliefs and social status of the voters. These points, for example, are only met in four of the fourteen polls that I have analyzed for the Andalusian elections. Even in these reliable polls, the difference between the direct intention and the estimate of the vote is attributed by many to “cooking” carried out with dark intentions. In reality, all serious surveys correct the results obtained in direct voting intention. Because?
The Direct Voting Intention (DIV) is the most immediate and spontaneous response when asking who would be voted for if the elections took place tomorrow. About 60% of those surveyed usually respond to this direct question, but we know that part of the other 40% finally goes to vote on election day. To obtain a faithful representation of the electoral result, it is necessary to assign a probable vote to those who do not answer the direct question. To do this, they are asked about the party with which they feel the most affinity or with which they identify to a greater extent: this response constitutes the “Sympathy” which, in the second column, is added to the IDV. For this column to be extrapolated as an estimate of results, the sample (the people surveyed) would have to exactly reproduce the universe of potential voters. Something impossible, since when selecting the sample it is not possible to know, a priori, the vote of the respondents, since it is secret. However, well-conducted surveys also ask about vote recall from past elections, which allows us to detect a non-representative sample (with more or fewer voters from a party than should be), or a hidden vote. In both cases, the results must be treated and corrected so that they resemble reality as closely as possible. This is where the famous “kitchen” of surveys comes in, which, if it is professional, is not only appropriate but essential. As long as an investigation is methodologically sound, with a representative sample and applies the pertinent post-survey adjustments to the data, it is possible to approximate a good forecast of the electoral results.
At Corporación 5-SAO we have our own methodology to make electoral estimates. Given that most polls commit biases and errors introduced by the sampling methodology of each polling agency, we use the poll aggregation technique, which allows us to work with a larger number of respondents and reduce volatility in predictions. Likewise, to avoid the biases and errors of the “kitchen” of each pollster, we work only with the unadjusted data, weighting them according to the number of respondents, the proximity to election day and the success of the pollster in the past.
With this methodology, we predict that the next Andalusian elections will be won by the PSOE, as announced by all the polls, but by a difference of just three percentage points with respect to the PP, while in the rest of the surveys the difference ranges between 5 and 10 p.p. Podemos obtains 18.4% of the votes, Ciudadanos 9.8% and IU 7.3%. The interviewed sample suffers a strong bias towards PSOE voters and to a lesser extent IU voters, while the PP seems underrepresented. Regarding Podemos and Ciudadanos, there is no memory of voting in the last Andalusian elections, but there is with respect to the European elections, which allows us to deduce that Podemos voters are overweighted, while Ciudadanos voters are very underrepresented in the sample.
U!
