The document discusses the key characteristics of a good measuring instrument: 1. Reliability - The instrument must provide consistent results. Factors like test length, age range, and time between tests impact reliability. 2. Validity - The instrument must accurately measure what it intends to measure. Factors like language, difficulty, evaluation methods can impact validity. There are different types of validity including content and construct validity. 3. Objectivity - Scores from the instrument must not depend on who administers or evaluates it. Objectivity can be measured by having multiple people score tests and comparing results.

1. Characteristics of a good measuring instrument
By
Dr.Neha Deo

2. Characteristics of a good measuring instrument
6.Usability
5.Adequacy
4.Discriminating
Power
3.Objectivity
2.Validity
1.Reliability
Good
Measuring
Instrument

3. 1. Reliability
Reliability-The reliability of the test refers to the
consistency of scores obtained by the same
individual at different occasions.
1st day scores obtained -47
After 7 days scores obtained for the same test
-47

4. 1. Reliability
• Methods to find out reliability
Test Retest method
Parallel tests method
Split half method
Kuder Richardson method
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5. 1. Reliability
• Factors affecting The reliability
• Length of the test –If length is more Reliability is high.
• Range of respondents ability –if it is greater, reliability is
high.
• Span of age group of respondents- If It is large,
reliability is high.
• Method of determining the reliability.
• Time span between two tests- If it is greater, then the
reliability is less.
• Way of evaluating the answers sheet-If it is objective,
then the reliability is high.

6. 1. Reliability
• Factors affecting The reliability
• Difficulty level high –Reliability is less.
• Language of the questions-If the language is
difficult, reliability is less.
• The way of answering –If it is done by guessing,
then the reliability is less.
• Environment –It also affects the validity.
• Optional questions-If optional questions are given,
reliability reduces.

7. 1. Reliability-effect of the time span in test retest
method.
Time Span R. coefficient
1 1 week 0.74
2 1 month 0.69
3 2 months 0.57
4 6 months 0.25

8. 2. Validity
• Validity is the authenticity of the test.
• The test should measure what it supposed to be
measured.
• If any test is fulfilling its objective then that is called as
the valid test.
• The concept of validity was formulated by Kelly (1927, p.
14) who stated that a test is valid if it measures what it
claims to measure.
• For example a test of intelligence should measure
intelligence and not memory.

9. 2. Validity
Factors affecting Validity-
Culture,
Ambiguous instructions.
Low level questions.
Medium of the Test (Language-whether mother tongue or
not) )
Questions based on the objective or not.
Improper variables.

10. 2. Validity
Factors affecting Validity-
Bias.
Time given
Way of answering.(By making guess or not)
Language of the test.(Easy , understandable of
not)
Difficulty level.
Evaluation method –objective/subjective.

11. 2. Validity
• Types of validity
Content Validity
Criterion related Validity
Concurrent validity
Construct validity

12. Absence o subjectivity is nothing but
objectivity.
There should not be any change in the scores
when the test is evaluated by different
supervisors.
To find out objectivity, the test is checked by
two different supervisors & coefficient of
correlation is found out.
3. Objectivity

13. 4. Discriminating Power
• The test should measure the small
differences in the respondents ability.
Index of item discriminating power
Ru+RL
D=------------------* 100
½ T
Ru= Number of the students in the upper group who answered
correctly.
RL=Number of the students in the lower group who answered
correctly.
T==total number of the students who tried the item
D= discriminating index.

14. 5. Adequacy
Adequacy also called as the
comprehensiveness of the test.
The test should measure the
variable comprehensively.

15. 6. Usability/Feasibility/Utility
The test prepared with taking efforts should be easy for
use.(user friendly).A usable test is
 Easy to use
 Scoring is easy.
 Economic
 Can be solved in a limited time.
 Interpretation is easy.
 Availability of parallel test.
 Easy to store.
 Should not require some special training.