Factors Affecting Reliability

Reliability is the degree to which an assessment tool produces stable and consistent results.

Factors Affecting Reliability

1. Length of the test. 
One of the major factors that affect reliability is the length of the test. A longer test provides a more adequate sample of behavior being measured and is less disturbed by chance factors like guessing.

2. Moderate item difficulty.
The test maker shall spread the scores over a quarter range than having purely difficult or easy items. Bloom’s taxonomy helps serve as the basis for equal distribution of difficulty. 

3. Objectivity.
Eliminate the biases, opinions or judgments of the person who checks the test. Socio-political beliefs shall be set aside when checking the test.

4. Heterogeneity of the students’ group.
Reliability is higher when test scores are spread out a range of abilities. Reliability is achieved when the test-takers represent a variety of intellectual levels and skills.

5. Limited time.
Speed is a factor and is more reliable than a test that is conducted at a longer time. This factor considers the chances that a student might cheat.

Asaad, Abubakar S. (2004). Measurement and evaluation concepts and application (third edition). 856 Mecañor Reyes St., Sampaloc, Manila. Rex Bookstore Inc.

Calmorin, Laurentina. (2004). Measurement and evaluation, 3rd ed. Mandaluyong City. National Bookstore Inc.