realibility

Reliability
Ed5-edu: Educational Measurement and Evaluation
Instructor: Stephen Jay Co

Reliability
 Common

threats to reliability

 Conventional methods for

estimating

reliability of test scores
 Techniques for

improving reliability

Reliability
 Reliability

is the degree to which a test measures something consistently.

 If

any assessment lacks reliability, it lacks validity.  Anything causes inconsistency within

measure is a potential threat to its reliability. the

Common threats to reliability
1.) Inconsistencies between earlier and later measures
 If students are administered tests before and after instruction, their performance normally changes.
 Example as students in third grade given an aptitude tests and again same test in their sixth grade. Inconsistent result in this case is desirable.

Common threats to reliability
2.) Inconsistencies between test items that supposedly measure the same skill
 Typically, a teacher will ask more than one test item to measure a skill being assessed in a written test.
 Inconsistency can come from;
◦ Guessing
◦ Vague questions
◦ Items designed for the same skill incorrectly measures a different skill



This inconsistencies are undesirable and threatens reliability of scores on these tests.

Common threats to reliability
3.) Inconsistencies between alternate skills in the same content domain
 The complexities of skills that are taught in the classroom create another source of inconsistency within student assessments.
 Example , assessing student ability to deliver a persuasive speech. inconsistencies such as topic for speech, instructional goal of the teacher or confidence and attitude of the student.
 Samples for assessment are not absolute. Our goal is to take steps in the development of student assessment to maximize the reliability.

Common threats to reliability
4.) Inconsistencies from measuring
unrelated