2.5. Study Attrition
We statistically investigated whether there were systematic differences between participants at all measurement points and those who responded less frequently. The tests showed that participants who responded at all measurement points were more often girls, enrolled in the general study track, and had higher socioeconomic status than the rest of the students. We also investigated whether there were significant differences in the outcome measures based on participation in all versus fewer measurement points. Pupils who responded at all measurement points experienced higher levels of class belonging and life satisfaction, less loneliness, higher grades, and less absenteeism, compared with those who responded less frequently. In contrast, we found that students who did not respond at one measurement point had more perceived teacher support than those who always responded. There was no difference between the pupils in terms of perceptions of a caring climate.