This document discusses the concepts of reliability and validity in measurement. Reliability refers to the consistency of a measurement and is assessed through stability and equivalence. Stability looks at consistency over repeated measurements using test-retest reliability and parallel forms. Equivalence examines consistency between two equivalent test forms using split-half reliability. Validity refers to how accurately an instrument measures a construct and is assessed through predictive validity, concurrent validity, and content validity.

1. RELIABILITY & VALIDITY

2. RELIABILITY
• Reliability means the consistency of
measurement.
• ie; The ability of a measuring instrument
to give accurate and consistent result
when repeated.
• Ex: A weighting scale is reliable, if it gives
the same reading when the same object
is weighted several times.

3. STABILITY & EQUIVALENCE are 2
aspects of reliability
Stability means, the same result
are obtained over repeated
measurement.
2 sets of Stability are
(1) Test – Retest Reliability
(2) Parallel form reliability

4. TEST-RETEST RELIABILITY
• It is used to assess the consistency of
measure at different times.
• ie: A test is given a set of people at
twice and see if the 2 sets of scores
are correlated.

5. • Ex: A group of respondents can test
their IQ scores.
• Each respondents is tested twice- the
2 tests are conducted one month
after the first one.

6. PARALLEL FORM/ALTERNATIVE
• It is used to assess the consistent
results of the 2 tests constructed in
the same way.
• ie; give everyone in a group 2 forms
of the same test and correlate those
2 sets of scores.

7. EQUIVALENCE
• SPILT- HALF RELIABILITY
• A test is conducted and the test is
divided into 2 halves and scored
separately.
• Then the score of one half of test are
compared to the score of the
remaining half of the test.

8. VALIDITY
• Validity means the effectiveness of an
instrument in measuring the specific
property.
• Any measuring instrument is valid when it
measures most accurately the objects.
• There is often direct and close connection
between the nature of the object measured
and the measuring instrument.

9. • if we are measuring physical properties like
height, weight, length then maintaining
validity is not a great problem, because
direct measuring devices are available.
• On the other hand, there are many social
characteristics which cannot be measure
directly
• Ex: such as Achievement, Attitude…

10. TYPES OF VALIDITY
• (1) Predictive validity
• (2) Concurrent validity
• (3) Content validity

11. (1) PREDICTIVE VALIDITY
• It is a useful test to predict the future
performance.
• If we are able to make accurate
predictions we can say that our
measuring instrument is valid.
• Ex: Reading readiness test might be
used to predict student’s achievement
in reading.

12. (2) CONCURRENT VALIDITY
• This test helps to distinguish individuals
who would differ in the future.
• The result of a new test are compared
with an established test, to see, if they
are well correlated.
• Ex: A new version of an IQ test correlate
with past versions.

13. (3) CONTENT VALIDITY
• This test helps to measure a
particular period or content.
• Ex: A semester exam that only
includes a 6 months portion.
• It is not a valid measure of the entire
course.

14. THANK U