Fig. 1

Frequencies of chosen response option—German population and cancer patients’ first assessment. The EORTC QLQ-C30 questionnaire was presented in two versions. The conventional questionnaire used mäßig and the optimized version used ziemlich as response option 3 (quite a bit) of the 4-point Likert scale. Responses to each response option (1–4) are presented for the total sample and are further separated for (1) subjects with QoL < 50 and QoL ≥ 50 as well as for (2) questionnaire version with response option mäßig and questionnaire version with response option ziemlich. German population: A total of N = 54,891 responses were given from N = 2033 respondents to items 1–27 (no missing responses). Cancer patients: At first assessment, a total of N = 12 089 responses were given from N = 450 patients to items 1–27 (missing responses n = 61 [0.5%])