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 Procedure
for assigning symbols,
letters, or numbers to empirical
properties of variables according to
rules.
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 Difficulty
in measuring concepts directly
(e.g., academic achievement)
 Usually
measure indicators of concepts (e.g.,
CGPA)
 Level
of measurement determines the type
of statistical analysis.
 The
level of measurement you use depends
on how you want to measure an outcome.
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 Nominal
 Ordinal
 Interval
 Ratio
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 Latin
word nomin (name)
 Variable categorical in nature
 Differ in quality not quantity (numbers have no
meaning only label)
 Characterizes
observation into one (and
only one) category  mutually exclusive
 Solely qualitative
 No obsolute zero (0)
 Matematical operation not possible.
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 Describes
variables that can be ordered
along some type of continuum.
 Not only categories, order as well.
 Ranking according to various outcomes,
e.g., big & little.
 No obsolute ‘0’, only relative position;
e.g., Zul is taller than Sheereen and
Sheereen is taller than Rozumah (no
information on how much taller).
 Matematical operation not possible.
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Latin word intervalum (spaces between walls).
 Describes variables that have equal intervals btw
them.
 Allow us to determine the difference btw points
along the same type of continuum (e.g., the
difference btw 300 and 400 is the same as the
difference btw 700 and 800; i.e., 100).
 0 is arbitrary (subjective, temporary).
 Simple matematical operation.
 More precise & convey > info than nominal &
ordinal; but must be cautious in interpreting.

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 Latin
word ratio (calculation).
 Describes variables that have equal intervals
btw them & have absolute 0.
 Most precise.
 Complex matematical operation.
 Highest level of measurement.
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1. Nominal
2. Ordinal
3. Ratio
A.
B.
4. Interval
C.
D.
Have a true zero
(highest level).
Categorical in
nature (lowest
level)
Have equidistant
points along some
underlying
continuum.
Are ranked.
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TYPES OF
MEASUREMENT
ON HEIGHT
1.
2.
3.
4.
Nominal
Ordinal
Ratio
Interval
A is 5 inches taller than B
(know precise
difference).
B.
Precise height measured
on a scale with true
zero.
C.
Categorize people into A
and B (people different
in height).
d. Tall and Short (have
some meaning, but
nature of difference is
not known).
A.
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 Nominal
level variables are categorical in
nature (lowest level)
 Ordinal -- are ranked.
 Interval -- have equidistant points along
some underlying continuum.
 Ratio -- have a true zero (highest level).
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Reliability and validity are the hallmarks of
good measurement.
Assessments tools must be reliable and valid,
otherwise the research hypothesis may be
incorrectly rejected.
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 Reliability
is a practical measure of how
consistent and stable a measurement instrument
or a test might be.
 Reliability
is often measured using the
correlation coefficient.
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 Dependency
 Consistency
 Stablility
 Trustworthiness
 Predictability
 Faithfulness
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1.
2.
3.
4.
Test-retest
Parallel forms
Inter-rater
Internal consistency
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A
measure of stability.
 Examines consistency over time.
 Administer the same test/measure at two
different times to the same group of
participants.
 Coefficient: rtest1.test2
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A
measure of equivalence.
 Examines consistency between forms.
 Administer different forms of the same test
to the same group of participants.
 Coefficient: rform1.form2
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A
measure of agreement.
 Examines consistency across raters.
 Have two raters, rate behaviors and
determine the amount of agreement
between them.
 Coefficient: % of agreement.
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A
measure of consistently each item
measures the same underlying construct.
 Examines reliability within a particular
set of item.
 Correlate performance on each item with
overall performance across participants.
 Coefficient: Chronbach’s alpha
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 Is
the quality of a test doing what it is designed
to do.
 The
test or instrument you are using actually
measures what you need to have measured.
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 Truthfulness,
 Accuracy
 Authenticity
 Genuineness
 soundness
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1.
2.
Content
Criterion
i.
ii.
3.
Concurrent
Predictive
Construct
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A
measure of how well the items represent the
entire universe of items
 Established
by asking expert if the items assess
what you want them to.
 History
test = test items ask questions on history
not Science.
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i.
Concurrent validity
 A measure of how well a test estimates a
criterion.

Established by selecting a criterion and
correlate scores on the test with scores
on ther criterion in the present.

Good student = test result + reports by
lecturers.
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ii. Predictive Validity

A measure of how well a test predicts a
criterion.

Select a criterion and correlates scores on the
test with scores on the criterion in the
future.

High merit on STPM/Diploma = Score high
CGPA.

Pass driving test = Good driver.
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
A measure of how well a test assesses some
underlying construct.

Assess the underlying construct on which the test
is based and correlate these scores with the
scores.

Theoretically and practically sound.

Intelligence test actually measures intelligence.
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A
test can be reliable without being valid
but the reverse is not true.
A
test can be reliable, but not valid, but a test
cannot be valid without first being reliable.


Reliablity is a necessary, but not sufficient, condition
of validity.
You are answering questions on simple addition, but
we called it spelling test! Obviously it is not a test on
spelling  lack of validity, does not affect reliability.
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