It took a while to find an actual explanation for the Polish data issues they mention. It's at the end of section 5 of the Reader's Companion document, under "Overall assessment of data quality" [0]. Click saver:
> In Poland, nine interviewers were identified as having a relatively large share of cases with unusual response patterns of respondents, using the same criteria that led to the identification of cases in the other countries. All data from these interviewers (774 cases in total) have been excluded from the data used to estimate the population model, which establishes the relationship between the variables from the background questionnaire and performance on the direct assessment to generate proficiency estimates (OECD, forthcoming[1]). This exclusion enhances the robustness of the model, by ensuring it is estimated based only on the cases considered to be of sufficient quality.
> Moreover, stronger evidence was collected that six of these interviewers in Poland breached data collection protocols throughout the survey. For instance, some of these interviewers were implausibly productive, conducting many interviews on a single day. Others did not record interviews or obtain respondents’ phone numbers, which made validation of interviews more difficult. Yet another interviewer was found to have falsified seven cases during data collection (cases which were immediately removed from the dataset as part of the quality-control process and are not included in the 774 cases under consideration in this note). Twenty-seven other cases collected from this interviewer were, however, validated and remained in the dataset. Since these factors raise concerns about the quality of all cases completed by these six interviewers, the responses to the cognitive assessment items for all cases of these six interviewers were excluded from the database (559 in total). Plausible values for these cases were then estimated using only their responses to the background questionnaire (for which no unusual patterns were detected) and the parameters estimated by the population model.
> In Poland, other cases with unusual response patterns that could suggest possible disengagement or lack of a reasonable level of effort during the assessment were identified. As these cases were not clustered within any particular interviewer, they were left in the dataset and treated as all other cases, given the difficulty of establishing objective criteria to determine whether reasonable effort was exerted, and whether the results of the assessment truly reflect the proficiency of respondents. While similar cases are present in all countries, the number of such cases in Poland can potentially have a significant impact on the estimated proficiency of the overall population. This should be kept in mind when interpreting Poland’s results. For this reason, in OECD (2024[3]) results for Poland are flagged with an asterisk.
Poland has a different viewpoint on what many other cultures would view as cheating. These paragraphs align with what I often see from Polish coworkers - not outright cheating but making adjustments here and there, even when totally unnecessary.
> In Poland, nine interviewers were identified as having a relatively large share of cases with unusual response patterns of respondents, using the same criteria that led to the identification of cases in the other countries. All data from these interviewers (774 cases in total) have been excluded from the data used to estimate the population model, which establishes the relationship between the variables from the background questionnaire and performance on the direct assessment to generate proficiency estimates (OECD, forthcoming[1]). This exclusion enhances the robustness of the model, by ensuring it is estimated based only on the cases considered to be of sufficient quality.
> Moreover, stronger evidence was collected that six of these interviewers in Poland breached data collection protocols throughout the survey. For instance, some of these interviewers were implausibly productive, conducting many interviews on a single day. Others did not record interviews or obtain respondents’ phone numbers, which made validation of interviews more difficult. Yet another interviewer was found to have falsified seven cases during data collection (cases which were immediately removed from the dataset as part of the quality-control process and are not included in the 774 cases under consideration in this note). Twenty-seven other cases collected from this interviewer were, however, validated and remained in the dataset. Since these factors raise concerns about the quality of all cases completed by these six interviewers, the responses to the cognitive assessment items for all cases of these six interviewers were excluded from the database (559 in total). Plausible values for these cases were then estimated using only their responses to the background questionnaire (for which no unusual patterns were detected) and the parameters estimated by the population model.
> In Poland, other cases with unusual response patterns that could suggest possible disengagement or lack of a reasonable level of effort during the assessment were identified. As these cases were not clustered within any particular interviewer, they were left in the dataset and treated as all other cases, given the difficulty of establishing objective criteria to determine whether reasonable effort was exerted, and whether the results of the assessment truly reflect the proficiency of respondents. While similar cases are present in all countries, the number of such cases in Poland can potentially have a significant impact on the estimated proficiency of the overall population. This should be kept in mind when interpreting Poland’s results. For this reason, in OECD (2024[3]) results for Poland are flagged with an asterisk.
[0]: https://www.oecd.org/en/publications/survey-of-adult-skills-...