According to Rosnow and Rosenthal, (2008), reliability is the one important criterion. In the most general terms, it implies consistency or stability, but it may also imply dependability. It is an important aspect of research in the human services. There are different types of reliability, alternate- form reliability: The degree of relatedness of different forms of the same test, (Rosnow & Rosenthal 2008). Internal – consistency reliability, the overall degree of relatedness of all items in a test or all raters in a judgment study (also called reliability of components). Item- to- item reliability, the reliability of any single item on average, analogous to judge to judge reliability, which is the reliability of any single judge on average. Test- retest reliability, the degree of temporal stability relatedness of a measuring instrument or test, or the characteristic it is designed to evaluate, from one administration to another; also called retest reliability,( Rosnow & Rosenthal, 2008). An example of test-retest reliability is when a test is given to students in a school to see where they stand in their studies and then retest them again a month later to see if they have improved or have stayed at the same level in their studies.
Validity is another important part of measurements and research. Validity is one of these criteria. In the most general terms, it shows how well the measure or design does what it purports to do. The measure in question might be a psychological test of some kind, a group of judges who rate things, a functional MRI scanner for monitoring brain activity, or any other instrument or measuring tool, (Rosnow & Rosenthal, 2008). There is several different types validity such as, construct validity, the degree to which the conceptualization of what is being measured or experimentally manipulated is what is claimed, such as the constructs that are measured by psychological tests or that serve as a link between independent and dependent variables, (Rosnow & Rosenthal 2008).Content validity is the adequate sampling of the relevant material or content that a test purports to measure (Rosnow & Rosenthal 2008). An example of content validity would be if there is a study to cumulate assessments of clients coming into a work force looking for work, within the questions there are complicated wording and phrases. The test can become one of comprehension, rather than just knowing what the client is looking for. Convergent and discriminant validity, the grounds established for a construct based on the convergence of related tests or behavior, convergent validity and the distinctiveness of unrelated tests or behavior, discriminant validity (Rosnow & Rosenthal 2008). . Criterion validity: the degree to which a test or questionnaire is correlated with outcome criteria in the present, its concurrent validity, or the future, its predictive validity,(Rosnow & Rosenthal 2008). An example of criterion validity would be when taking a group of unbiased social workers that say they can handle child abuse very well. The study will take a larger group of people and will give them a questionnaire of hundreds of questions related to child abuse. The questionnaires will be analyzed and researcher will identify those that are