Table 1 Coding scheme

Odd wording

Respondent indicates that he/she finds used terms or phrases odd or unusual

Difficult wording

Respondent indicates that he/she is unfamiliar with terms or phrases or struggles with a complicated structure

Difficult interpretation of item

Respondent expresses that he/she does not know or understands what is meant by the item

Wrong interpretation of item

Respondent has something else in mind when interpreting the item than intended by the developers

Narrow interpretation of item

Respondent focuses on one aspect of the construct or expresses insecurity about the focus of the item, where the intention of the developers is to cover a broad range of the construct (either due to double-barrelled items or broad multidimensional concepts)

Different answers for different aspects of item

Respondent expresses that different response options apply to different aspects of the construct (e.g. low physical control but high cognitive control) (and therefore has to choose to answer just one aspect or an average answer)

Response options partly applicable

Respondent indicates that one part of the response option fits to his/her situation but the other part not

Irrelevant response option(s)

Respondent indicates that it is impossible/unlikely that one of the response options will be chosen

Missing intermediate response option

Respondent expresses that there is a gap between two consecutive response options

Similar response options

Respondent indicates that in his/her perspective (the value of) response options is/are similar

Disagreement with order of response options

Respondent expresses or shows that the order of the response options is not in agreement with his/her perspective

Positive responding

Respondent chooses a more positive answer than what an outsider would, based on what is known by this outsider about the respondent’s life.