Fixed alternative questions are closed-ended and have exact answers. Open-ended are unstructured and provide less direction to the responder. Open-ended questions are used more in qualitative studies to allow a more basic understanding of the topic. Indexes and scales are components of questionnaires. Indexes relate a number of questions to provide a more thorough measurement of selected variables.
Scales deal with the structure of the questionnaire items.
Different types of scales are used to measure different types of variables. Likert, Thurstone, and Guttman are three of the better known scales used in the measurement of social variables. The use of existing instruments is acceptable for many reasons. The reasons include such things as prior validity and reliability, reduced time and money devoted to instrumentation, and prior data to compare data generated from subsequent study. Sometimes, existing instruments can be revised to allow for usage with a newer study.