PYC4807 Assignment 3
(PORTFOLIO COMPLETE
ANSWERS) 2023 (255701) -
DUE 29 September 2023.
, QN 1
Reliability and validity are two essential psychometric properties used to evaluate the quality
of a test or measurement instrument. They assess different aspects of the test's
performance and characteristics. Here's a brief differentiation between the two:
Reliability (2 marks):
Reliability refers to the consistency, stability, and repeatability of the test scores or
measurements obtained from a particular instrument. In other words, it measures the extent
to which a test produces consistent results when administered multiple times to the same
individuals under the same conditions. A reliable test should yield similar results if the
underlying construct being measured remains unchanged.
There are different types of reliability, including:
Test-retest reliability: The degree of consistency in scores when the same test is
administered to the same group of participants at two different time points.
Internal consistency reliability: The extent to which different items within the test (e.g.,
questions or statements) consistently measure the same construct.
Inter-rater reliability: The degree of agreement among different raters or observers when
scoring or interpreting the test results.
Validity (2 marks):
Validity, on the other hand, is concerned with the accuracy and appropriateness of
inferences and interpretations based on the test scores. It assesses whether the test
measures what it claims or intends to measure. In essence, validity evaluates the extent to
which the test actually measures the construct or trait it is supposed to measure.
There are several types of validity, including:
Content validity: The degree to which the test items represent a comprehensive and relevant
sample of the construct being measured.
Criterion validity: The extent to which the test scores can predict or correlate with a specific
external criterion or outcome related to the construct.
Construct validity: The overall validity of the underlying theoretical construct that the test
aims to measure.
In summary, reliability focuses on the consistency of test scores, while validity assesses the
accuracy and appropriateness of what the test measures. A test can be reliable (consistent)
but not valid (measuring the wrong thing), but a valid test must also be reliable to ensure that
the measurements are consistent and dependable.
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