This document discusses the concept of reliability in assessment. Reliability refers to the consistency, stability, and dependability of scores from an assessment. There are several ways to estimate reliability, including test-retest reliability (measuring consistency over time), equivalent forms (using two similar tests), and internal consistency (measuring how items on a single test correlate with each other). Common measures of internal consistency are Cronbach's alpha and item-total correlations. Factors like test length, administration conditions, and time between tests can impact an assessment's reliability. Ensuring clear directions, an adequate number of test items, and limited delays between test administrations can help improve reliability.

1. Celine Espada

3. Like validity, the term
reliability has been used for
many years to describe an
essential characteristic of
sound assessment.

5. RELIABILITY
Concerned with the
consistency , stability and
dependability of the scores.

6. FREE FROM BIAS AND
DISTORTION THE
ASSESSMENT IS.
TEACHERS MIGHT ASK
THEMSELVES:

7.  Do I have enough
information about the
learning of this particular
student to make a
definitive statement?

8.  • WAS THE
INFORMATION
COLLECTED IN A
WAY THAT GIVES
ALL STUDENTS AN
EQUAL
CHANCE TO SHOW
THEIR LEARNING?

9.  Would another
teacher arrive at the
same conclusion?

10. Would I make the same
decision if I considered this
information at another time
or in another way?

11. ESTIMATES OF RELIABILITY?

12. 1.MEASURE OF STABILITY
OR RETEST

13. Test-retest reliability is
usually measured by computing
the correlation coefficient
between scores of two
administrations.

14. 2.MEASURE OF
EQUIVALENCE
The equivalent form of estimate
reliability obtained by giving two
forms of a test to the same group of
individuals on the same day and
correlating the result.

15. Advantages
• Eliminates the problem of memory effect.
• Reactivity effects (i.e., experience of taking
the test) are also partially controlled.
• Can address a wider array of sampling of the
entire domain than the test-retest method

16. Possible Disadvantages
• Are the two forms of the test
actually measuring the same thing.
• More Expensive
• Requires additional work to develop
two measurement tools.

17. 3.MEASURE OF INTERNAL
CONSISTENCY
• Measures the reliability of a test solely
on the number of items on the test and
the inter-correlation among the items.
Therefore, it compares each item to
every other item.
• If a scale is measuring a construct,
then overall the items on that scale
should be highly correlated with one
another.

18. • There are two common ways of
measuring internal consistency
1. Cronbach’s Alpha:
.80 to .95(Excellent)
.70 to .80 (Very Good)
.60 to .70 (Satisfactory)
<.60 (Suspect)

19. 2. Item-Total Correlations -
the correlation of the item
with the remainder of the
items (.30 is the minimum
acceptable item-total
correlation).

20. Split Half - refers to determining
a correlation between the first
half of the measurement and the
second half of the measurement
(i.e., we would expect answers to
the first half to be similar to the
second half).

21. Possible Advantages
• Simplest method - easy to perform
• Time and Cost Effective
Possible Disadvantages
• Many was of splitting
• Each split yields a somewhat different reliability
estimate
• Which is the real reliability of the test?

22. FACTORS AFFECTING
RELIABILITY

23. • Poor or unclear directions given
during administration or inaccurate
scoring can affect reliability.
For Example - say you were told that
your scores on being social
determined your promotion. The
result is more likely to be what you
think they want than what your
behavior is.

24. • The larger the number of items, the greater
the chance for high reliability.
For Example -it makes sense when you
ponder that twenty questions on your
leadership style is more likely to get a
consistent result than four questions.
• Remedy: Use longer tests or accumulate
scores from short tests.

25. For Example -If you took an instrument in
August when you had a terrible flu and then
in December when you were feeling quite
good, we might see a difference in your
response consistency. If you were under
considerable stress of some sort or if you
were interrupted while answering the
instrument questions, you might give
different responses.

26. • The shorter the time, the greater the chance for high
reliability correlation coefficients.
• As we have experiences, we tend to adjust our views a
little from time to time. Therefore, the time interval
between the first time we took an instrument and the
second time is really an "experience" interval.
• Experience happens, and it influences how we see
things. Because internal consistency has no time lapse,
one can expect it to have the highest reliability
correlation coefficient.

27. THANK YOU