Final answer:
Questions used in a subject-completed instrument can be classified as either closed-ended or open-ended items. Closed-ended questions collect quantitative data with predetermined response options, while open-ended questions collect qualitative data with subjective and varied responses.
Step-by-step explanation:
Questions used in a subject-completed instrument can take many forms but are classified as either closed-ended or open-ended items. Closed-ended questions have predetermined response options like yes-or-no or multiple-choice, collecting quantitative data. Open-ended questions require short essay responses and collect qualitative data that is subjective and varies from person to person.