Reliability&Validity

First, Lets define Reliability and Validity…

Reliability refers to how consistently a method measures something.
Validity measures what it claims to measure.

WHY VALIDITY AND RELIABILITY IS IMPORTANT TO ASSESSMENT?

Why so?

For that reason, validity is the most important single 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. Reliability is also an important component of a good test. After all, an assessment would not be very valuable if it was inconsistent and produced different results every time.

Reliability and Validity are just like Paper and Printer. They can work as a great team!

There is an important relationship between reliability and validity. An assessment that has very low reliability will also have low validity clearly a measurement with very poor accuracy or consistency is unlikely to be fit for its purpose. But, by the same token, the things required to achieve a very high degree of reliability can impact negatively on validity.

TYPES OF RELIABILITY AND VALIDITY

Test-retest

This is characterized by the replicability of results. That is to say, if a group of students takes a test twice, both the results for individual students, as well as the relationship among students’ results, should be similar across tests.

Inter rater

This needs two or more rater to evaluate the test in order to be more accurate.

Internal Consistency

Analogous to content validity and is defined as a measure of how the actual content of an assessment works together to evaluate understanding of a concept.

Construct

This ensures the interpretability of results, thereby paving the way for effective and efficient data-based decision making by school leaders.

Content

This is not a statistical measurement, but rather a qualitative one. For example, a standardized assessment in 9th-grade biology is content-valid if it covers all topics taught in a standard 9th-grade biology course.

Criterion

This refers to the correlation between a test and a criterion that is already accepted as a valid measure of the goal or question. If a test is highly correlated with another valid criterion, it is more likely that the test is also valid.

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