Reliability refers to the consistency of a measure. There are several types of reliability: test-retest, equivalency, inter-rater, and internal consistency. Test-retest reliability assesses consistency over time, equivalency assesses consistency between parallel forms, inter-rater assesses consistency between raters, and internal consistency assesses consistency between items. Factors like memory, practice effects, and maturation can impact reliability over time. Reliability is important for a measure to be valid and useful. Ways to improve reliability include making tests longer, carefully constructing items, and standardizing administration procedures.
A measurable characteristic that varies and may change from group to group, person to person, or even within one person over time.
Variable is a logical grouping of attributes, characteristics or qualities that describe an object. It may be either height, weight, anxiety levels, body temperature, income and so on.
Variable is frequently used in quantitative research projects pertinent to define and identify variables.
A variable incites excitement in any research than constants as it facilitate accurate explanation of relationship between the variables.
The present ppt will help the student to get the idea of response set or bias. The ppt will help the learner to understand various types of biases and techniques for controlling them.
A measurable characteristic that varies and may change from group to group, person to person, or even within one person over time.
Variable is a logical grouping of attributes, characteristics or qualities that describe an object. It may be either height, weight, anxiety levels, body temperature, income and so on.
Variable is frequently used in quantitative research projects pertinent to define and identify variables.
A variable incites excitement in any research than constants as it facilitate accurate explanation of relationship between the variables.
The present ppt will help the student to get the idea of response set or bias. The ppt will help the learner to understand various types of biases and techniques for controlling them.
This short SlideShare presentation explores a basic overview of test reliability and test validity. Validity is the degree to which a test measures what it is supposed to measure. Reliability is the degree to which a test consistently measures whatever it measures. Examples are given as well as a slide on considerations for writing test questions that demand higher-order thinking.
This short SlideShare presentation explores a basic overview of test reliability and test validity. Validity is the degree to which a test measures what it is supposed to measure. Reliability is the degree to which a test consistently measures whatever it measures. Examples are given as well as a slide on considerations for writing test questions that demand higher-order thinking.
Reliability refers to how consistent and stable your research results are ,and how well they can be replicated by other researchers. Validity refers to how well your research measures what it intends to measure, and how accurately it reflects the reality of the phenomenon you are studying,
Reliability
Reliability refers to the extent to which a scale produces consistent results, if the measurements are repeated a number of times.
Reliability is a measure of the stability or consistency of test scores.
When a measurement procedure yields consistent scores when the phenomenon being measured is not changing
Degree to which scores are free of “Measurement Error Consistency of the measurement
Example: Weighing scale used multiple times in a day by the same individual
Types of reliability
Internal consistency reliability
Test-retest reliability
Split–half method
Inter-rater reliability
Internal consistency reliability
Also known as inter-item reliability.
It is the measure of how well the items on the test measure the same construct or idea.
Cronbach's Alpha
Cronbach's Alpha are most commonly used used to measure inter-item reliability to see if questionnaires with multiple questions are reliable. Value must by above 0.7.
Test-retest reliability
Test-retest reliability is a measure of reliability obtained by administering the same test twice over a period of time to same group of individuals.
Test-retest reliability is the degree to which scores are consistent over time.
Same test- different times
Example: Administering the same questionnaire at 2 different times such as IQ test.
Split–half method
A method of determining the reliability of a test by dividing the whole test into two halves and scoring the two halves separately.
Especially appropriate when the test is very long.
The most used method to split the test into two is using the odd-even strategy.
Inter-rater reliability
Inter-rater reliability is the extent to which two or more raters (or observers, coders, examiners) agree.
Inter-rater reliability is essential when making decisions in research and clinical settings.
References
Neuman, L. (2014). Social Research Methods: Qualitative and Quantitative Approaches. Pearson Education Limited.
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2. Introduction
• In the psychometrics, reliability is the overall
consistency of a measure.
• A measure is said to have a high reliability if
it produces similar results under consistent
conditions.
• For example, measurements of people’s
height and weight are often extremely
reliable
3. Definition of Reliability
• Reliability is defined (Portney and
Watkins, 2000) as:
‘the extent to which a measurement is
consistent and free from error’.
6. Test-retest reliability-
• assesses the degree to which test scores are
consistent from one test administration to the next.
• It involves:
Administering a test to a group of individuals
Re-administering the same test to the same group at
some later time
Correlating the first set of scores with the second
8. Assumption of the method
• Number of item in the test are large therefore
memory, practice, and carry over will not effect the
retest scores.
• Innate ability of an individual remains constant so
the growth and maturity will not effect the retest
score.
• Time gap of retest score should not be more than six
month.
9. Advantage
• It is the most simplest and easy method of
estimating reliability coefficient
• It is the most appropriate method of estimating
reliability of speed test but it is adequately used for
speeded test.
• It is an economical method of reliability is one form
of the test is used on both times.
10. Limitation
• This method is less accurate
• It is time consuming method of reliability
• The individual΄s health, emotional condition,
motivational conditions, mental health and mental set
do not remains the same in both the administrations.
11. Equivalency reliability
• assesses the degree to which test scores are
consistent when there is a variation in the methods or
instruments used.
• This method of reliability is known by various name
or terms such as parallel form of reliability ,
alternative forms reliability, equivalent forms of
reliability, and comparable – forms reliability
13. • Criteria for Equivalency reliability
The number item should be the same
The item variance should be the same
There should be equivalence with regard to content,
types of items, the range of difficulty value.
Instructional procedure of administering the tests
should be the same
14. Assumption
• The memory, practice and carry over factors do not
effect the scores
• Two forms of a test are virtually alike with reference to;
a) Difficulty and discrimination indexes
b) Content and type of item
c) Size number of items
d) Time of administration
15. Advantage
• The method of reliability is an improvement over the
test retest method of reliability
• The practice, memory, exercise, and maturity effect
are controlled in this method.
• It is an economical and speedy method for
calculating reliability coefficient.
• It is useful for the reliability of achievement tests
16. Limitation
• It is difficult to construct parallel form of test and
satisfy all the conditioned mentioned.
• Interval for administration the two forms will not be
more than two weeks.
19. Internal consistency reliability
• Internal consistency reliability assesses the consistency of
results across items within a test.
• The most popular method of testing for internal
consistency in the behavioral sciences is coefficient alpha
• There are a wide variety of internal consistency measures
that can be used.
a) Average inter-item correlation
b) Split-half reliability
20. Average inter-item correlation
• Average inter-item correlation is a subtype of internal
consistency reliability.
• It is obtained by taking all of the items on a test that
probe the same construct (e.g., reading
comprehension), determining the correlation
coefficient for each pair of terms, and finally taking
the average of all of these correlation coefficients.
22. Split half method of reliability
• It involves:
Administering a test to a group of individuals
Splitting the test in half in two equal parts
Correlating scores on one half of the test with scores
on the other half of the test
• The common way of dividing the test item is the
odd and even numbers.
23.
24. Spearmen –brown prophecy formula-
R= 2 rxy
1+rxy
R=reliability of whole test
rxy= correlation of x (odd) and y (even) series.
25. Assumption
• It assumes that items of the test is homogeneous. All
the items of the test measure the same trait or ability
• The assumption of for splitting test in to two halves
that these are equivalent
26. Advantages
• All the limitation of earlier methods are eliminated in
this method- memory, carry over, practice skills,
maturity factor.
• When the parallel forms of a test are not advisable
and repetition is not possible, this method is
employed to compute reliability of test.
27. Limitation
• Chance factors may effect scores on the two halves of the
test in the same way; it tends to make the reliability index
too high.
• A test can be divided in two parts in a number of ways, so
that the reliability coefficient is not a unique.
• It is not possible to divide the test in two halves in such a
way that both are equivalent.
• This method cannot be used in power test and
heterogeneous test.
28. Sources of error
Item Sampling
Construction of the Items
Test administration
Scoring
Difficulty of the Test
Student Factor
29. Factors that contribute to
consistency
• stable characteristics of the individual or the attribute
that one is trying to measure.
30. Factors that contribute to
inconsistency:
• Temporary but general characteristics of the
individual: health, fatigue, motivation, emotional,
strain
• Temporary and specific characteristics of individual:
comprehension of the specific test task, specific
tricks or techniques of dealing with the particular test
materials, fluctuations of memory, attention or
accuracy
31. • Aspects of the testing situation: freedom from
distractions, clarity of instructions, interaction of
personality, sex, or race of examiner
• Chance factors: luck in selection of answers by sheer
guessing, momentary distractions
32. Satisfactory level of reliability
• A satisfactory level of reliability depends on how a
measure is being used.
• The standard is taken from Nunnally (1978), who
suggests that in the early stages of research on predictor
tests or hypothesized measures of a construct, reliabilities
of .70 or higher will be sufficient. scores,
• Nunnally (1978) recommends that a reliability of at least
.90 is desirable, because a great deal depends on the exact
score made by a person on a test.
33. Relationship between reliability
and validity
• Validity and reliability are closely related
• A test cannot be considered valid the measurements
resulting from it are reliable. Likewise, results from a
test can be reliable but not necessarily valid.
• While a reliable test may provide useful valid
information, a test that is not reliable cannot possibly
be valid
34.
35. Ways to improve reliability
• Write longer tests.
• Pay more attention to the careful construction of
the test questions.
• Start planning the test and writing the items well
ahead of the time the test is to be given.
• Write clear directions and use standard
administrative procedures.
