Page 93 - DEDU504_EDUCATIONAL_MEASUREMENT_AND_EVALUATION_ENGLISH

Unit 7 : Reliability – Types , Methods and Usability

Where, MS ind = Average class of deviation of individual’s average scores Notes
MS resi = Average class of variation of remaining items after deducting items and
individual variation

A test does not become a speed test by merely specifying the time limit, because if
all students are able to complete the test within the specified time limit, then there
is no reason for a student to increase his speed, and on the contrary, if a student is
not able to complete the test, then it is not possible to measure his speed accurately.

7.4 Usability of Reliability

The reliability of an assessment tool is the extent to which it consistently and accurately measures
learning.
When the results of an assessment are reliable, we can be confident that repeated or equivalent
assessments will provide consistent results. This puts us in a better position to make generalised
statements about a student’s level of achievement, which is especially important when we are
using the results of an assessment to make decisions about teaching and learning, or when we are
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 educators
should always be prepared to question results.
Factors which can affect reliability :
• The length of the assessment — a longer assessment generally produces more reliable
results.
• The suitability of the questions or tasks for the students being assessed.
• The phrasing and terminology of the questions.
• The consistency in test administration — for example, the length of time given for the
assessment, instructions given to students before the test.
• The design of the marking schedule and moderation of marking procedures.
• The readiness of students for the assessment — for example, a hot afternoon or straight after
physical activity might not be the best time for students to be assessed.

What is K-R Coefficient ?

Self Assessment
2. State whether the following statements are ‘true’ or false’.
(i) The chief basis of ascertaining reliability is correlation.
(ii) The reliability coefficient obtained from the method of rational equivalence is also called
coefficient of internal consistency.
(iii) The higher the reliability coefficient (r) between two tests, the less reliable is the test in
test retest method.

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