In psychotherapy research, treatment efficacy is commonly studied by means of self-report questionnaires to gain quantitative data on symptom development. The data serve as input for statistical analyses up to the level of evidence-based treatment. We analyzed how a patient in a psychotherapy study experienced the translation of her story into quantitative data by combining a phenomenological qualitative analysis of her therapeutic narrative and a visual analysis of her extensively annotated paper-andpencil questionnaires. Our findings provide a practical empirical illustration of (...) the nature and impact of known validity issues. Beyond, we found the act of questionnaire administration affected the primary complaint such that it became performative toward the symptoms under study. We discuss the epistemic consequences for the validity of data, and we argue that valid data collection requires qualitative scrutiny of meaning within data and a concept of validity that allows for consideration of performativity of data collection. (shrink)