Validity

[Judith Bell - Doing your research project (p104)]

Validity is an altogether more complex concept. It tells us whether an item measures or describes what it is supposed to measure or describe. If an item is unreliable, then it must also lack validity, but a reliable item is not necessarily also valid. It could produce the same or similar responses on all occasions, but not be measuring what it is supposed to measure.

Tell other people what you are trying to find out or to measure and ask them whether the questions or items you have devised are likely to do the job. You need to achieve some degree of reliability and validity in question wording. Your aim to obtain as representative a range of responses as possible to enable you to fulfil the objectives of your study and to provide answers to key questions.