Your position
In this PhD project, you will assess the statistical validity of psychological intervention studies. You will apply a wide range of state-of-the-art meta-scientific techniques to studies in the domain of medical and clinical psychology. Your project can have immediate impact by proposing concrete ways to improve practices in psychological intervention studies. This interdisciplinary PhD project lies at the intersection of methodology and statistics on the one hand, and medical and clinical psychology on the other hand. A rough outline of the project would entail:

Project 1: Conduct a systematic review describing often used analysis models testing psychological interventions and if/how flexibility in data analysis is prevented in accompanying preregistrations.
Project 2: Run simulation studies to assess whether the models found in Project 1 provide unbiased estimates of a true intervention effect and whether power analyses with these models would result in substantially different minimum sample sizes than the required sample size reported in the studies from Project 1 .
Project 3: Assess the effect of statistical variability of (un)published intervention effects in practice, by re-analyzing all available data on a specific psychological intervention of your own choosing.
Project 4: Synthesize the findings of projects 1 and 3 by providing a set of guidelines to increase the statistical validity of psychological intervention studies.
You are encouraged to make this research your own, by choosing your own specific focus and project implementations. We highly value your input and creativity.
 

Research context
You will work under direct supervision of dr. Paul Lodder, dr. Michèle Nuijten,  and prof. dr. Jelte Wicherts .You will be part of the Meta-Research Center (https://metaresearch.nl), a renowned research group working on a variety of topics within meta-research in psychology (i.e. publication bias, meta-analysis, causal inference, p-hacking, preregistration, qualitative research). You will have ample opportunity to collaborate within the research group, and you are encouraged to seek collaborations outside the Meta-Research Center as well, for example with the department of Medical and Clinical Psychology.

Your assessment of the statistical analysis of psychological interventions can have direct impact on the way researchers analyze intervention effects in psychology. You are encouraged to actively share your findings and recommendations through scientific papers and conferences, but also through channels such as blog posts, social media, and news outlets. 

We strongly value open science: among other things, we encourage preregistration, sharing of data and materials, and we facilitate open access publication.
Beside research, you will also contribute to the teaching tasks within the department. 

Background
Myriad studies in medical and clinical psychology investigate the effectiveness of psychological interventions in improving the mental health of patients with various physical diseases or mental disorders. Despite the fact that researchers testing psychological interventions are generally interested in similar research questions (i.e., is intervention A more effective than intervention B in improving mental health?), they can answer them using a wide range of methodological designs of varying quality. Even the methodological gold standard of intervention research, the randomized controlled trial, can be threatened by the “degrees of freedom” researchers have when analyzing their data. For most published intervention studies it remains unclear whether different statistical models would have produced similar conclusions. In this PhD project, you will aim to answer this question.