Conciseness | A global health instrument must be concise and is obtained from one question or a restricted number of questions (eg, branch-and-stem format, several items combined). Conciseness should be evaluated in terms of survey time required to answer the question(s). |
Simplicity of the question(s) | A global health instrument has to be easily grasped by respondents. The cognitive burden on the respondent should be as low as possible. The grammar and concepts used in the language of reference (ie, English) should have equivalents in other target languages. The simplicity (or complexity) of a question is best assessed qualitatively using cognitive and field tests. It can also be evaluated during the design phase using the best practice of questionnaire design. Simplicity can be assessed using: the number of clauses, the number of words per clause, the inclusion of low frequency words (ie, words which are not often used in everyday life language, such as ‘participation’), the presence of vague or imprecise relative terms (eg, ‘seldom’), the presence of vague or ambiguous noun phrases (such as abstract nouns which have unclear or ambiguous referent), or the syntax. |
Usability for general population surveys | A global health instrument should be relevant to the adult population targeted in surveys, often individuals aged 15 years or older. |
Amenability to multi-modes of collection | A global health instrument should be useable in self-administered surveys and applicable to telephone and face-to-face interviews, with no intervention from the interviewer. It should be compatible with proxy responses, that is, responses given on behalf of the selected respondent. The mode and proxy effects should be considered when designing the instrument and assessed during the test phase. |