ABSTRACT
This chapter discusses the two technical aspects of test design: reliability and validity. Reliability is the foundation of the usefulness of a test. If the reliability of a test is too low it cannot be used to explain or predict behaviour. Test-retest reliability looks at changes in the test scores. It is clear that mental toughness scores can change, but it is important these changes are attributable to some form of intervention or identifiable action. The Mental Toughness Questionnaire 48 (MTQ48) was carefully designed to have appropriate items, have a relatively low reading age and have a simple rating system. The MTQ48 provides a reliable measure of mental toughness. The model of mental toughness it measures has clear theoretical roots and appears to offer a solid understanding of what mental toughness means. The MTQ48 is acceptable to a wide range of people and there are seldom any issues about its applicability. End users find it appropriate and can understand the items.
