Is the extent to which a test measures what it is supposed to measure and it is the most important consideration in test evaluation?
The reliability of an assessment tool is the extent to which it consistently and accurately measures learning. Show
The validity of an assessment tool is the extent by which it measures what it was designed to measure. Reliable assessment results will give you confidence that repeated or equivalent assessments will provide consistent results. This puts you in a better position to make generalised statements about a student’s level of achievement, especially when you are using the results of an assessment to make decisions about teaching and learning, or reporting back to students and their parents or caregivers. No results, however, can be completely reliable. There is always some random variation that may affect the assessment, so you should always be prepared to question results. Factors that can affect reliability:
How to be sure that a formal assessment tool is reliableCheck in the user manual for evidence of the reliability coefficient. These are measured between zero and 1. A coefficient of 0.9 or more indicates a high degree of reliability. Assessment tool manuals contain comprehensive administration guidelines. It is essential to read the manual thoroughly before conducting the assessment. ValidityEducational assessment should always have a clear purpose, making validity the most important attribute of a good test. The validity of an assessment tool is the extent to which it measures what it was designed to measure, without contamination from other characteristics. For example, a test of reading comprehension should not require mathematical ability. There are several different types of validity:
A valid assessment should have good coverage of the criteria (concepts, skills and knowledge) relevant to the purpose of the examination. Examples:
There is an important relationship between reliability and validity. An assessment that has very low reliability will also have low validity. A measurement with very poor accuracy or consistency is unlikely to be fit for its purpose. However, the things required to achieve a very high degree of reliability can impact negatively on validity. For example, consistency in assessment conditions leads to greater reliability because it reduces 'noise' (variability) in the results. On the other hand, one of the things that can improve validity is flexibility in assessment tasks and conditions. Such flexibility allows assessment to be set appropriate to the learning context and to be made relevant to particular groups of students. Insisting on highly consistent assessment conditions to attain high reliability will result in little flexibility, and might therefore limit validity. The Overall Teacher Judgment balances these ideas with a balance between the reliability of a formal assessment tool, and the flexibility to use other evidence to make a judgment. Further readingArticles from NZCER SET magazine - Set 2, 2005 and Set 3, 2005 - written by Charles Darr. Used with permission. Is the extent to which a test measures what it is supposed to measure?Validity refers to the degree to which a test measures what it is supposed to measure.
Is the extent to which a test measures what it claims to measure it is vital for a test to be valid in order for the results to be accurately applied and interpreted?Validity is the extent to which a test measures what it claims to measure. 1 It is vital for a test to be valid in order for the results to be accurately applied and interpreted. Psychological assessment is an important part of both experimental research and clinical treatment.
What refers to the extent to which a test does the job for which it is used?Test validity. Validity is the most important issue in selecting a test. Validity refers to what characteristic the test measures and how well the test measures that characteristic. Validity tells you if the characteristic being measured by a test is related to job qualifications and requirements.
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