A Generalization of the «Lady-Tasting-Tea» Procedure to Link Qualitative and Quantitative Approaches in Psychiatric Research

Bruno Falissard, Daniel Milman, David Cohen


Abstract: In Fisher’s “The Design of Experiments”, a trial was designed to test a lady’s claim to be able to discriminate whether the milk or the tea was added first to a cup. In this trial, eight cups are poured, four with milk first and four with tea first. They are then presented in random order to a subject who has to divide them into two sets of 4, according his/her belief about the "treatment" received. The present paper generalizes this design so that a hypothesis concerning the existence of two sub groups in a set of psychiatric patient records (whether written, audiotaped or videotaped) can be tested rigorously from a statistical point of view. Tables are proposed to enable power and sample size calculations. A real example is presented; it shows that psycho-dynamically oriented professionals are able to discriminate seven healthy adults who have experienced a sibling’s cancer during childhood or adolescence from seven matched controls. This method is particularly suited to small sample studies that explore elusive clinical hypotheses traditionally tackled with qualitative methodologies.


Randomization, power calculation, permutation test, clinical records

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ISSN: 1929-6029