1. School of Natural Sciences, University of Patras, 26504 Rion, Greece
2. School of Humanities, Hellenic Open University, 26335 Patras, Greece
3. Turku Research Institute for Learning Analytics, University of Turku, FI-20014 Turku, Finland
4. Department of Educational Sciences and Early Childhood Education, University of Patras, 26504 Rion, Greece
5. Department of Computer Engineering and Informatics, University of Patras, 26504 Rion, Greece