Informers in the Stapel case speak out

In an interview with Dutch newspaper de Volkskrant, three students who brought the fraud of Tilburg University professor Diederik Stapel to light speak openly but anonymously about their experiences. During their research at the School of Social and Behavioral Sciences, these students grew suspicious towards the way Stapel attained his data.

With the positive first impression the students had of their professor, the junior researchers initially did not doubt the perfect correlations in their professor’s research. The students grew more suspicious after studying the data of a research allegedly preformed at a high school. After confronting Stapel with the age of the students in the research – some of them were 19 years old –  he replied that  the research had probably been performed at a university. Some inconsistencies in the figures were assumed to be typos.

What started out as a joke about the unlikeness of the perfect correlations, turned into more concrete signs of fraud. With a growing suspicion on the reliability of Stapel’s data, one of the students decided to measure the Cronbach’s Alpha. This number offers insight in the consistency in answers given in questionnaires. Where an Alpha of more than 0.9 is to be expected in a reliable research, Stapel’s research had an Alpha of 0.45. This led to the belief that the data in this research was fictitious.

Aware of the possible consequences of making their suspicions known, the students decided to perform further calculations on Stapel’s experiments. After repeatedly finding different and less perfect relations than Stapel did, the students decided to bring their findings out in the open and confront their professor.


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