Validity And Reliabilty

This presentation was developed for the
exclusive use of students enrolled in:

Educational Testing & Grading,
Professor Gregory E. Stone.

© 2004 Gregory E. Stone. All rights reserved. This presentation may not be
reproduced in any form, in part or as a whole, without the express written permission
of the author.

Exam Score
Quality

Validity & Reliability

No matter how well the
objectives are written,
or how clever the items,
the quality and usefulness
of an examination is
predicated on Validity
and Reliability


Evaluative

Examination Score
Quality

Statistical


Validity

Examination Score
Quality

Reliability


Validity
BOTH CONCEPTS
RELATE TO THE
SCORE NOT
THE TEST!

Reliability


Validity Reliability
We don’t say “an exam is valid and reliable”

We do say “the exam score is reliable and
Valid for a specified purpose”

KEY ELEMENT!


Reliability
“Was the measure of student
ability reached by accident or
chance, or was it reached through
a clear and stable, meaningful
examination?”


Reliability
Answers questions relative to
the stability and clarity of an
examination.


Reliability
Reliability is a STATISTIC.
Specifically, a correlation
ranging from
0 = Completely Unreliable
1 = Perfectly Reliable


Reliability
Reliability is also a measure of
error within an examination.

Poor wording, ambiguity,
correct answer issues, failure
to link with objectives, etc.

Content/
Action + Error


The information we seek and our
best hope for obtaining it.

Content/
Action + Error


The information we seek and our
best hope for obtaining it.

Content/
Action + Error
Our human frailty and inability to
write effective questions.


Reliability
Reliability comes in multiple
forms, including:

Test-Retest Reliability
Split-Half Reliability


Reliability
Test-Restest
Administer to students.
After time, administer again.

Are the students performing in
a consistent manner?

Reliability
Split-Half
Create 2 smaller content
Balanced tests and administer.

Do students perform similarly
on each test half?

Validity
“Did the test we created really
measure what we hoped it
would measure?”


Validity
Relates to questions about the
reasonability of content,
criterion and construct
associated with the learning
objectives and assessment.


Validity
Content Related Validity

Does the content we have selected
appropriately represent our
construct (top level domain)?


Validity
Construct Validity

Is there really such a concept as
what we created as a construct?
(e.g. Does “reading ability” really
exist?)

Validity
Criterion Related Validity

Does our test adequately link the
content to the construct?
Is the test a good measure of the
construct?

Validity

Examination Quality

Reliability


RELIABILITY
is a necessary but
not sufficient condition for
VALIDITY


Validity And Reliabilty

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