How are the surveys conducted?

Through surveys, we can learn about citizens' opinions, attitudes, and behaviors. But how are they conducted?

1. The topic

   To conduct a survey, it is first necessary to select the topic and objectives that the research will address.

   The CIS has conducted surveys on a wide variety of topics: employment, education, youth, healthcare, national and international politics, religion, gender, civic values, etc.

2. The universe and the sample

   Secondly, we must define the reference population (which we call the universe) and make a representative selection from this population (which we call the sample).

   The sample design, that is, the selection of people for the survey, is crucial, as it allows the data obtained to be used to describe and analyze the sample population, the universe. It is important to keep in mind that a sample has a margin of error, the magnitude of which is established in the technical sheet that accompanies each study and specifies all the technical characteristics.

3. The size

   The sample size and characteristics vary depending on the objectives of the survey. The CIS typically works with large samples, which vary depending on the purpose of the study.

4. Writing the Questionnaire: How do you ask the questions?

   The questionnaire includes a series of questions to gain insight into the selected topic. It also asks about the interviewees' characteristics (gender, age, educational level, occupation, marital status, income, etc.).

   The CIS technical staff develops the questionnaires based on careful documentation, which includes consulting previous studies conducted by the CIS, as well as those conducted by other institutions and international organizations dedicated to conducting surveys.

   When designing the questions, special care is taken to ensure that all of them are clear and understandable to the interviewees, regardless of their educational level or any other characteristic. We also ensure that they are objective and impartial, and do not incorporate any bias in their wording that could influence or influence the respondents' responses.

   There are other questionnaire questions that are open-ended, meaning they don't have predetermined answers. In this case, respondents are asked to express, in their own words, whatever opinion they deem appropriate. For example, in the monthly barometers, respondents are asked what they believe to be Spain's three main problems. They respond freely, and the interviewers must record their answers verbatim. All these responses are then categorized (what is called the "coding process"). This makes it possible to group responses that refer to, for example, "unemployment," "housing," or "healthcare." This allows the number of mentions of each of these topics to be counted.

5. Data collection or fieldwork

   Data collection – also called “fieldwork” – consists of administering a questionnaire to all selected individuals.

   In 2020, the lockdown imposed as a result of COVID-19 prompted a shift from an in-person model to a telephone model. The telephone survey was conducted using the CATI (Computer-Assisted Telephone Interviewing) system, which allows for a record of interviewees' direct responses.

   The telephone numbers used by the CIS in its studies are randomly generated, with nine-digit mobile and landline numbers. A robot dials them and verifies whether these numbers actually exist and belong to individuals. The interviewers do not choose the numbers to call, nor do they have any information about them. An automated system makes the calls and offers them the contact. This avoids selection bias.

   Citizen collaboration is always voluntary and essential to ensure that survey results accurately reflect the opinions of society as a whole. All responses are anonymous and protected by statistical secrecy and personal data protection laws.

6. Data processing

   Once data collection is complete, all the information is processed to obtain detailed results and analyze the public's opinions on the topic under study.

   All responses provided by the interviewees are recorded anonymously in a data file or matrix.

   The data obtained are processed (tabulated) and published on the CIS website, which is accessible to anyone. These documents have a provisional version known as "preliminary results." The data file is subsequently reviewed and subjected to a verification and cleaning process.

   The CIS Research Department is the unit that plans and carries out these studies. The Database Department verifies, classifies, stores, and safeguards the data from the studies conducted. As a result of the use of new information and communications technologies, a new Information and Communications Technology Department was created in 2022, tasked with promoting digital transformation and innovation applied to public opinion research.