Reliability

[Judith Bell - Doing your research project (p103)]

Whatever procedure for collecting data is selected, it should always be examined critically to assess to what extent it is likely to be reliable and valid. Reliability is the extent to which a test or procedure produces similar results under constant conditions on all occasions. Checking is not necessary unless you are attempting to produce a test or scale. The check for reliability will come at the stage of question wording and piloting of the instrument.