Election surveys: Science or séance?

will then be not face to face, but by phone by simply dialing the randomly chosen numbers. Appropriate replacement methods are employed in anticipation of unanswered calls, or people refusing to participate in the survey. However, this may not produce a reliable and representative sample when applied in the Philippines, since it effectively excludes people without mobile phones. This then violates the principle of randomization where every member of the population must have an equal and fair chance of being chosen.

In the end, the usual practice in the Philippines is to adopt a stratified random sampling, where the unit being sampled are individual voters drawn from randomized locations such as cities/municipalities, barangays, households and voting precincts. Here, the sampled 1,800 voters are distributed proportionally to the different regions, after which the sampling points in each region are drawn by randomly choosing first the sample municipalities/ then randomly drawing from each municipality/ city the sample then randomly drawing from each barangay either the sample household, or the sample precincts.

If the lowest sampling unit is a sample precinct, it is just a matter of drawing randomly from the registered voter’s list of that precinct. Ideally, this is the best method that can approximate perfect randomization since if done properly, this ensures that every voter has an equal chance of being drawn as a sample considering that all geographical units, from municipalities/cities to to precincts were all given equal chance to be chosen, and that the number of samples per region is proportional to the voting population of that region.

However, when the lowest sampling unit is a household, then some bias might enter the process in the identification of who in the household to interview. If the method chosen is the head of the household, then certainly this violates the basic principle of a truly random sample since it now then effectively eliminates other members from being part of the sample. One other method is simply to consider the first person who answers the door who is also an eligible voter. While this is an improvement, it nevertheless has a bias against people who may be working, or who are regularly away from home.

One method that is also used that can magnify the bias, and therefore undermine the reliability and validity of the survey, is when the lowest sampling unit is drawn not from a voters list from a randomly chosen precinct in a sampled barangay, but a house

- ization, but spatially from a land-

center in the sample barangay. In this method, the surveyor, using some heuristic guide, would draw the sample respondent relative to the landmark, by setting a distance and a direction, and then drawing the sample household to the landmark. This can be the

voter who answers the door, or the head of the household of the house located in that spot. This method is extremely problematic considering the bias it holds in favor of those living near landmarks, even as it carries with it the inherent structural biases that are associated when the individuals are not drawn from a voters list.

- didates have accused surveys of being biased, and of being designed only to condition the minds of people to create a bandwagon effect, or of being blatant partisan strategies to manipulate voter preferences. It is therefore incumbent upon survey organizations like SWS, Pulse Asia and PUBLiCUS, among others, to also help in educating the public about the science of surveys. And they can do this by being transparent, and by publishing in detail every time they release a survey the location of their samples. It is not enough to simply publish the number of respondents from the four geographical locations of NCR, balance Luzon, Visayas and Mindanao. In addition, they should also indicate the detailed methodology of how they eventually chose their sampled respondents. It is only through these that they can dispel the doubts of the voters, and make them realize that they are scientists communicating the results of a statistically reliable

not spiritualists who communicate the results of their séance with the dead and the imagined.