Data analysis
Data were analyzed using multilevel modeling to account for the nested data structure with repeated measurements (Level 1) nested within individuals (Level 2). For our hypotheses targeting intervention effects, individual Formal model description:Level 1: (within participants)
Level 2: (between participants)


For the hypotheses on the association between daily stress and sleep parameters, the dependent variable (fitbit-measured sleep duration, subjective sleep duration, or sleep quality) was predicted by stress reported on the previous evening (Level 1: (within participants)
Level 2: (between participants)


