Study Design

Sample. A general shortcoming of the thesis refers to the samples used in the three studies.

Although the thesis aimed to model SRL for college students in general, the heterogeneity of the sample can be regarded as a limitation because participants studied different subjects and had different levels of study experience. Moreover, the samples were predominantly female as a result of the participants’ subjects of study (e.g., psychology, languages, etc.). With regard to study I, the heterogeneity of the sample is not a real limitation as the results of the trait model underline SRL’s importance for college students irrespective of their subject of study and experience level. Concerning gender effects, it would be interesting to examine if the model fits for both genders as there are some differences in central variables. Whereas males report higher self-efficacy (Huang, 2013) and a higher use of elaborative learning strategies (Bembenutty, 2007), females show higher academic delay of gratification (Bembenutty, 2007). With regard to study II, the heterogeneity of the sample reduces the comparability of intervention groups as the distribution of subjects of study and experience was not the same within the four intervention groups. It is possible that the effects would have been different if all groups were sampled of f. ex. psychology students. Nevertheless, the results found with this heterogeneous sample are in favor of the training and learning diary’s usefulness for all groups of college students and therefore have a high external validity. Concerning study III, it is somewhat problematic that the cluster sample and the training sample differ with regard to study subject and university experience. This lowers the generalizability of differential effects found with the training sample. Nevertheless, SRL profiles could be confirmed in the training sample as well speaking in favor of their transferability to different subgroups of students.

An additional shortcoming of the samples used is the size of the training samples. In study II, participants had to be matched using propensity score matching to obtain comparable baseline values of SRL. Matching resulted in the elimination of several participants and

therefore the group size varied between n = 27 and n = 55. These sizes constitute the lower border of required cell size for multivariate ANOVA. Moreover, the cell sizes were not equally distributed. Therefore, larger sample sizes for the intervention groups and a more equal distribution could have result in a higher power of analyses (Bortz, 2005). Additionally, the quality of study III lacks from the relatively small sample size of the training group and the cluster groups in training. Therefore, power was reduced and possible effects (e.g., the increase for the low SRL with moderate motivation group) were not found. Thus, future studies should aim to investigate differential effectiveness with larger samples to receive more reliable results. Moreover, a larger sample would allow for investigating the combination of SRL profiles with personality profiles and an examination of how they interact in training.

Quasi-experimental design. An additional limitation mainly concerns the design of

study II and the realization of the factorial combinations. As a randomized assignment of participants to intervention groups was not possible and preexisting groups were used to realize the interventions groups, sample characteristics such as subject of study or college experience decrease the groups’ comparability. Although propensity score matching was used to make the groups comparable with regard to pretest SRL, ruling out possible confounding variables can only be realized through randomized control studies that have more statistical power and are easier to interpret. Nevertheless, sampling about 200 college students and assigning them randomly to a training or a control group seems difficult with regard to students’ motivation and time they are willing to invest in an educational study. The use of waiting control-groups would be one possibility to equal the effort of all study subjects.

No active control group. A further shortcoming is related to this realization of the

intervention groups: The control group received no intervention and therefore was a passive control group. Adding an active control group that takes part in an intervention with no SRL content would be useful to rule out possible Hawthorne effects (Bortz & Döring, 2006). Nevertheless, participants of the training groups were not informed of the study design or of

the existence of other groups. Besides that, the possibility of a Rosenthal effect due to trainer behavior that varies between condition and that supports effects for the combined group is rarely given due to the standardization of training.

Follow-up test. Although study II integrated a follow-up test to measure the

intervention effects’ stability, it would have been more interesting to conduct this follow-up test after college exams and after students received feedback on their achievement. As mastery experiences represent the most important source for the development of self-efficacy (Bandura, 1986), information on how the newly acquired strategies work during the preparation for exams would have resulted in more exact ratings of SRL. In addition, follow- up assessments for control groups would have been interesting as well to rule out possible time lagged effects (in particular for the learning diary only group).