**Slovenian Probability Panel**

The Slovenian Probability Panel is a pool of adult Slovenian residents who were recruited from the population register via** probability sampling** (a.k.a. **random sampling**) and who have consented in advance to participate in online surveys.

The Slovenian Probability Panel is primarily used for surveys in the academic and public sectors, where a higher quality of results is required. Due to the probability sample, relatively high participation rate and rigorous implementation of surveys, the panel provides **unbiased survey estimates** of population parameters with high degrees of confidence.

Surveys in the Slovenian Probability Panel are conducted online, but can also be supplemented with **mixed-mode survey methods** (eg. postal surveys).

The Slovenian Probability Panel is managed by the Centre for Social Informatics (CSI) at the Faculty of Social Sciences, University of Ljubljana, which also develops the online survey tool 1KA.

In case of interest, the Slovenian Probability Panel infrastructure can also be used to conduct a survey based on **a new probability sample**, i.e. outside the Slovenian Probability Panel, or in the context of a new recruitment wave when participation is particularly high. This is especially applicable considering that probability samples of the general population are nowadays predominantly conducted online.

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**Web Panels**

Online survey modes have revolutionised survey research and the survey industry (see Callegaro et al., 2015). Online surveys have become the dominant survey mode, while at the same time making surveys much simpler, faster, cheaper and more accessible. Today, virtually any internet user can develop an online survey (not just specialised agencies as in face-to-face or telephone surveys). As a result, the number of surveys has increased exponentially.

On the other hand, **recruiting** people to participate in online surveys is becoming increasingly difficult, mainly due to declining participation, rising costs (respondents need to be rewarded) and growing privacy concerns. In this context, **web panels** have emerged where people agree to regularly participate in various online surveys in exchange for certain rewards. This eliminates the need to recruit respondents for each individual survey.

The vast majority of online panels do not control the likelihood of people being included in such panels. In this case, we are talking about **commercial **or **non-probability web panels **(a.k.a. access panels), which recruit people to the panel in a variety of ad hoc ways (e.g. online, through another survey).

However, for more complex surveys in the public, non-profit and academic sectors, **probability web panels** have been set up in most developed countries, which select respondents probabilistically/randomly (e.g. from a population register) and therefore do not involve any volunteers. For details, see Vehovar & Čehovin, 2022.

**Probability Samples**

Probability web panels, such as the Slovenian Probability Panel, are based on a probability sample, where each unit in the population has a known and positive probability of being included in the sample (Kalton & Vehovar, 2021, p. 11). Probability samples typically require a list of all units; in the case of the general population, this is usually the population register or a list of all postal addresses in the country.

Probability samples are a prerequisite for generalisation or **statistical inference** from a sample to a population, i.e. for calculating confidence intervals and testing assumptions. If the sample is not probability-based, then generalisation to the population is in principle not possible and the associated risk is unknown.

Non-probability samples (and also non-probability panels) where we do not know the probability of a unit's inclusion are faster and cheaper than probability samples, but give less accurate estimates. Many comparative studies have been carried out (e.g. Cornesse et al., 2020; Mercer & Lau, 2023; Dutwin & Buskirk, 2017) which have uniformly shown that estimates derived from probability panels are significantly more accurate than those from non-probability panels.

**Mission of the Slovenian Probability Panel**

The **mission of the Slovenian Probability Panel **is to provide a low-cost **(non-profit**) infrastructure for conducting online surveys based on a **probability sample** and the highest **methodological standards**.

The Slovenian Probability Panel was piloted in 2022 for the purposes of the* Probability web panels in national statistics for persons and households *project*, *which is testing the potential of a probability web panel for national statistics, and the* Evaluating probability and non-probability online panels *project*, *which is developing an integrated approach for comparing probability and non-probability web panels.