ABSTRACT
The value of a study depends on the contribution that the study makes to science through the sustainability of its results and theoretical ideas. The time perspective easily disappears when the choices that were made in a longitudinal study are discussed. Five recommendations are presented based on the authors' experiences by utilizing the article by Pulkkinen and Kokko. After each recommendation, the solutions found in the JYLS are described and reflected upon. The first recommendation is to carefully consider whether one has a research problem for which a longitudinal study is really needed. The second recommendation is to consider whether research problems concern phenomena that are sustainable, independent of the theoretical constructs used for their interpretation. The third recommendation concerns the careful choice of a sample by weighing up different viewpoints. The fourth recommendation concerns the choice of measures. The fifth recommendation is to use advanced statistical methods for data analysis.
