SummaryListen to the passage. For questions 26—30, complete the notes using no

Summary
Listen to the passage. For questions 26—30, complete the notes using no more than three words for each blank.
Reliability and validity are key concepts in any form of enquiry. Reliability is a measure of consistency. For example, if a clock is sometimes fast and sometimes slow, it is unreliable. If a questionnaire produces different results for the same group of people each time it is used, then the questionnaire is unreliable. Validity is a measure of truth. It is possible for a questionnaire to be highly reliable yet invalid, like a clock which is always ten minutes slow. In contrast, a clock which is always right provides a valid and reliable measure of time. Similarly, a questionnaire which really measures what it claims to measure is a valid questionnaire. We can assess how valid our questionnaire is by comparing its results with an independent measure. For instance, if we ask people how often they visit their local theatre and then check the results against ticket sales, we will know how valid our questionnaire is. However often independent measures are themselves unreliable and of low validity. Furthermore in many cases there are no independent measures. In other words, a "true" answer (so)does not exist.