Diary study design
The main research questions addressed in diary studies are person- level information, within person change and individual differences over time, and causal analysis of within personal and individual differences.
Nevertheless, no matter its research goal, diary studies are characterized by collecting information through aggregation of data. Traditionally, data gathering was made using single reports, which converted the information obtained in an important source of bias due to the retrospective factor, since people tend to show a limited ability …show more content…
As data comes from repeated measures of the same participant, these measures cannot be assumed to be independent from each other. By averaging the whole set of aggregated results, within person variability would be much lower than what actually it is. The use of multilevel models solves the problem by correcting this downward bias in within person variability. At the time to deal with between person variability, multilevel models are also useful in order to eliminate upward bias. Between persons variability comes from the inter individual comparison of participants distribution, nonetheless as it is common to find significant changes in within person variability over time it is high probable that the estimated sample distribution have more variability than the real