validity reliability and feasibility

1. VALIDITY, RELIABILITY AND
FEASIBILITY
JASNA. PT
M. Phil., Scholar
Gandhigram Rural Institute-DU
Gandhigram

2. INTRODUCTION
 The Validity, Reliability and Feasibility of a test
is important for data collection process.
 Before and after collecting the data, the
researcher need to consider the validity,
reliability and feasibility of their data.

3. VALIDITY
 Indicate the degree to which an instrument
measures what it is supposed to measure
 It is the extent to which differences found with a
measuring instrument reflect true differences
among those being tested
 For a test to be reliable it also need to be valid

4. TYPES OF VALIDITY
1. Content Validity( Sample Validity)
2. Construct Validity
3. Criterion-related Validity

5. CONTENT VALIDITY
 Measuring instrument provides adequate
coverage of the topic under study
 Entire range or universe of the construct is
measured
 Usually evaluated and scored by experts in the
content area

6. CONSTRUCT VALIDITY
 It implies using the construct correctly
 It seeks agreement between a theoretical concept
and a specific measuring device or procedure
 Associate a set of other propositions with the
results received from using our measurement
instrument

7. CRITERION-RELATED VALIDITY
 Used to predict future or current performance
 It correlates test results with another criterion of
interest

8. FACTORS AFFECTING VALIDITY
1. Environmental factors
2. Research factors
3. Instrumentation factors
4. Subject factors

9. CONT….
 Environmental factors: Some environmental
factors such as room temperature, lighting and noice
can influence the error rate
 Research factors: The researcher can influence the
results of the study in many ways
 Instrumentation factors: An inadequate sampling
of items is the other common source of
instrumentation errors.
 Subject factors: Any changing physical, emotional
or psychological state of the subject could introduce
error into the measurement process.

10. RELIABILITY
 It is the degree to which an assessment tool
produces stable and consistent results
 A measure can be reliable without being valid,
but it cannot be valid without being reliable.

11. TYPES OF RELIABILITY
1. Test-retest Reliability
2. Parallel forms Reliability
3. Split half Reliability

12. TEST-RETEST RELIABILITY
 Obtained by administering the same test twice
over a period of time to a group of individuals.
 The scores are tabulated and the correlation
calculated
 Correlation is higher there will be more
reliability

13. PARALLEL FORMS RELIABILITY
 Different versions of an assessment tool to the
same group of individuals
 Both versions must contain same construct, skill,
knowledge etc.,

14. SPLIT HALF RELIABILITY
 “Splitting in half” all items of a test that are
intended to probe the same area of knowledge in
order to form two “sets” of items
 Items are divided into two halves and then
compared. Odd, even items, or 1-50 and 51-100
are two ways to split items

15. FACTORS INFLUENCING RELIABILITY
 Time interval between testing
 Condition under which measure
 Length of test
 Difficulty of the test

16. CONT….
 Time interval between testing: testing with
shorter intervals resulting in the higher
reliability coefficient
 Condition under which measure: Favorable
conditions will give high reliability coefficient

17. CONT….
 Length of test: The longer the test, higher the
reliability due to the fact that longer test will
provide more adequate sample of the behavior
being measured
 Difficulty of the test: tests that are too easy or
too difficult for the group members taking it
will tend to provide score of low reliability

18. RELATIONSHIP BETWEEN
VALIDITY AND RELIABILITY
 Validity and reliability are closely related
 A test cannot be considered valid unless the
measurements resulting from it are reliable
 Likewise result from a test can be reliable and
not necessarily valid

19. PRACTICALITY
 It refers to the economy of time effort and money in
testing. I other words a test should be…
 Easy to design
 Easy to administer
 Easy to mark
 Easy to interpret(the results)