Maartje Boer

CHAPTER 7 210 Interpretation of Trajectories Table 7.3 reports the model estimates and group sizes of the classes from the 4-class solution and Figure 7.3 shows the estimated means of problematic SMU and SMU frequency. In the first class, adolescents reported relatively high levels of problematic SMU ( M T1 = 2.430). Their level of problematic SMU followed a non-linear trend, whereby problematic SMU first increased, but decreased after T2. Adolescents in Class 1 also reported higher levels of SMU frequency than adolescents in the other classes ( M T1 = 5.264). The course of their SMU frequency was non-linear, whereby they first showed an increase, followed by a decrease. In Class 2, which had the least members (15.8%), the average level of problematic SMU was also relatively high, but stable over time ( M T1 = 1.973). Adolescents within this group, however, reported average levels of SMU frequency and this level remained stable over time ( M T1 = 3.628). In Class 3, adolescents reported the lowest level of problematic SMU, which was stable over time ( M T1 = 0.233). Also, adolescents’ SMU frequency was lower than average, with no significant changes over time ( M T1 = 2.249). In Class 4, which included themost members (37.1%), adolescents’ level of problematic SMUwas also lower than average and stable over time ( M T1 = 0.515), but the level of SMU frequency over time was higher than in Class 2 and 3, with a significant non- linear course: SMU frequency increased, but this increase became smaller over time and eventually decreased in T4 ( M T1 = 4.186). Table 7.3 Model Estimates 4-class Solution Class 1: n = 350 (24.7%) Variably high problematic SMU, variably high SMU frequency Class 2: n = 224 (15.8%) Persistently high problematic SMU, persistently average SMU frequency Class 3: n = 318 (22.4%) Persistently low problematic SMU, persistently low SMU frequency Class 4: n = 527 (37.1%) Persistently low problematic SMU, variably high SMU frequency B SE D. B SE D. B SE D. B SE D. Problematic SMU Intercept 0.888*** 0.084 a 0.680*** 0.165 a -1.458*** 0.212 b -0.665*** 0.131 c Slope 0.164 0.089 a 0.017 0.150 a 0.310 0.256 a 0.128 0.182 a Quadratic -0.064* 0.031 a -0.011 0.053 a -0.062 0.088 a -0.037 0.060 a SMU frequency Intercept 5.264*** 0.128 a 3.628*** 0.269 b 2.249*** 0.089 c 4.186*** 0.116 b Slope 0.592*** 0.137 ac -0.027 0.294 ab 0.077 0.106 b 0.711*** 0.119 c Quadratic -0.197*** 0.042 a 0.023 0.083 b 0.054 0.037 b -0.174*** 0.036 a Notes. SMU = social media use; B = unstandardized coefficient; SE = standard error; D. = difference, columns with different letters denote that estimates differed significantly across the respective classes as obtained by z -scores of the parameter differences. *** p < 0.001, p ** < 0.01, * p < 0.05;