Background: Data from the Programme for the International Assessment of Adult Competencies (PIAAC) revealed that countries systematically differ in their respondents' literacy, numeracy, and problem solving in technology-rich environments skills; skill levels also vary by gender, age, level of education or migration background. Similarly,…

In the past decades, the importance of developing and validating informal and nonformal learning processes has been launched by several international organizations including UNESCO and the OECD, originally mostly focusing on adult learning experiences. Meanwhile, in recent years an increased focus has been evidenced on introducing informal and…