How to address concerns about validity reliability and bias in assessments
The reliability of an assessment tool is the extent to which it consistently and accurately measures learning.
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 reliable
Check 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.
Educational 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.
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.
Articles from NZCER SET magazine - Set 2, 2005 and Set 3, 2005 - written by Charles Darr. Used with permission.
How can you improve reliability and validity of assessment?
Here are six practical tips to help increase the reliability of your assessment:.
Use enough questions to assess competence. ... .
Have a consistent environment for participants. ... .
Ensure participants are familiar with the assessment user interface. ... .
If using human raters, train them well. ... .
How can you reduce bias in an assessment?
Strategies to Minimize Confirmation Bias One of the best ways to guard against confirmation bias is to grade “blind,” or to block the names of the students you are grading until after you've assessed their work.
Should teachers be concerned about validity and reliability?
An understanding of validity and reliability allows educators to make decisions that improve the lives of their students both academically and socially, as these concepts teach educators how to quantify the abstract goals their school or district has set.