The poll field work, oversight and analysis was conducted and provided by Datexco Company S.A., a Colombia-based polling firm currently working in 10 countries in Latin America.  Datexco is certified by the International Organization for Standardization.   

The population under study was Salvadorans at least 18 years old, who had a voting ID card and intended to vote in the next presidential elections.

The poll surveyed a nationwide, multi-stage stratified conglomerate sample. Each municipality was stratified in large zones covering them in its entirety.  In each zone mapping areas were selected that were conglomerates of blocks and the blocks were clusters of houses.  In each area cartographic starting points were selected, in each selected point apple axis were made, so as to say that if the entire block is visited and the sample is not completed, we continued with the eight blocks surrounding the initial block. 

After identifying a household, the interviewer asked for the head of the household and whether they are registered to vote.  If not, then they go to the next eligible voter within the household or move onto the next household.  If there are multiple heads of the household or eligible voters then the interviewer asked who was willing to take part in the poll and picked one participant.

Sample size: 818

Eligibility criteria: age 18 and older

Response rate: of 25 percent, one in every household responded to the questionnaire

The margin of error is +/- 3.43 percent occurrence phenomena equal to or greater than 50 percent with a level of confidence of 95 percent.

Face-to-face interviews were conducted.
 
The nationwide poll was conducted December 5-12, 2008.