Measurement Scales, Reliability, Validity Explained

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Measurement: Scaling,
Reliability, Validity
CHAPTER 7

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Chapter Objectives
 Know the characteristics and power of the
four types of scales- nominal, ordinal,
interval, and ratio.
 Know how and when to use the different
forms of rating scales and ranking scales.
 Explain stability and consistency and how
they are established.
 Discuss what “goodness” of measures means,
and why it is necessary to establish it in
research.

Scale
 Is a tool or mechanism by which
individuals are distinguished as to how
they differ from one another on the
variables of interest to our study.
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scales
 There are four basic types of scales:
1. Nominal Scale
2. Ordinal Scale
3. Interval Scale
4. Ratio Scale
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scales
 The degree of sophistication to
which the scales are fine-tuned
increases progressively as we move
from the nominal to the ratio scale.
 The information on the variables can be
obtained in greater detail when we
employ an interval or a ratio scale than
the other two scales.
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scales
 With more powerful scales,
increasingly sophisticated data
analyses can be performed, which in
turn, means that more meaningful
answers can be found to our research
questions.
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Nominal Scale
 A nominal scale is one that allows the researcher to assign
subjects to certain categories or groups.
 What is your department?
O Marketing O Maintenance O Finance
O Production O Servicing O Personnel
O Sales O Public Relations O Accounting
 What is your gender?
O Male
O Female
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Nominal Scale
 For example, the variable of gender,
respondents can be grouped into two
categories- male and female.
 Notice that there are no third
category into which respondents
would normally fall.
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Nominal Scale
 The information that can be
generated from nominal scaling is to
calculate the percentage (or frequency)
of males and females in our sample of
respondents.
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Example 1
 Nominally scale the nationality of
individuals in a group of tourists to a country
during a certain year.
 We could nominally scale this variable in the
following mutually exclusive and
collectively exhaustive categories.
American Japanese
Russian Malaysian
Chinese German
Arabian Other
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Example 1
 Note that every respondent has to fit
into one of the above categories and
that the scale will allow computation of
the numbers and percentages of
respondents that fit into them.
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Ordinal Scale
 Ordinal scale: not only categorizes variables in such
a way as to denote differences among various
categories, it also rank-orders categories in some
meaningful way.
 What is the highest level of education you have
completed?
O Less than High School
O High School/GED Equivalent
O College Degree
O Masters Degree
O Doctoral Degree
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Ordinal Scale
 The preference would be ranked ( from
best to worse; or from first to last) and
numbered as 1, 2, 3, and so on.
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Example 2
 Rank the following five characteristics
in a job in terms of how important they
are for you.
You should rank the most important
item as 1, the next in importance a 2,
and so on, until you have ranked each
of them 1, 2, 3, 4, or 5.
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Example 2 (Cont.)
 Job Characteristic Ranking
The opportunity provided by the job to:
1. Interacts with others _____
2. Use different skills _____
3. Complete a task to the end _____
4. Serve others _____
5. Work independently _____
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Example 2 (Cont.)
 This scale helps the researcher to
determine the percentage of
respondents who consider interaction
with others as most important, those
who consider using a number of skills
as most important, and so on. Such
knowledge might help in designing jobs
that would be seen as most enriched by
the majority of the employees.
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Example 2 (Cont.)
 We can see that the ordinal scale
provides more information than the
nominal scale. Even though differences
in the ranking of objects, persons are
clearly known, we do not know their
magnitude.
 This deficiency is overcome by interval
scaling.
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Interval Scale
 Interval scale: whereas the nominal
scale allows us only to qualitatively
distinguish groups by categorizing them
into mutually exclusive and collectively
exhaustive sets, and the ordinal scale to
rank-order the preferences, the
interval scale lets us measure the
distance between any two points on the
scale.

Interval scale
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© 2009 John Wiley & Sons Ltd.
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Example 3a
 Indicate the extent to which you agree
with the following statements as they
relate to your job, by circling the
appropriate number against each,
using the scale given below.
strongly disagree 1, Disagree 2
Neither Agree Nor Disagree 3
Agree 4, Strongly Agree 5.
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Example 3a (Cont.)
 The following opportunities offered by
the job are very important to me:
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Interacting with others 1 2 3 4 5
Using a number of
different skills
1 2 3 4 5
Completing a task from
beginning to end
1 2 3 4 5
Serving others 1 2 3 4 5
Working independently 1 2 3 4 5

Example 3a (Cont.)
 Suppose that the employees circle the
numbers 3, 1, 2, 4, and 5 for the five items.
 The magnitude of difference represented
by the space between points 1 and 2 on the
scale is the same as the magnitude of
difference represented by the space between
points 4 and 5, or between any other two
points. Any number can be added to or
subtracted from the numbers on the scale,
still retaining the magnitude of the difference.
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Example 3a (Cont.)
 If we add 6 to the five points on the
scale, the interval scale will have the
numbers 7, 8,….., 11 ( instead of 1 to
5).
 The magnitude of the difference
between 7 and 8 is still the same as
the magnitude of the difference
between 9 and 10. It has an arbitrary
origin. 23

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Example 3b
 Circle the number that represents your feelings at this particular
moment best. There are no right or wrong answers. Please answer
every question.
1. I invest more in my work than I get out of it
I disagree completely 1 2 3 4 5 I agree completely
2. I exert myself too much considering what I get back in return
3. For the efforts I put into the organization, I get much in return

Ratio Scale
 Ratio scale: overcomes the
disadvantage of the arbitrary origin
point of the interval scale, in that it has
an absolute (in contrast to an arbitrary)
zero point, which is a meaningful
measurement point.
 What is your age?
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Ratio Scale
 The ratio scale is the most powerful
of the four scales because it has a
unique zero origin ( not an
arbitrary origin).
 The differences between scales are
summarized in the next Figure.
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The differences between
scales
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Developing Scales
 The four types of scales that can be used
to measure the operationally defined
dimensions and elements of a variable are:
Nominal, Ordinal, Interval, and Ratio
scales.
 It is necessary to examine the methods of
scaling (assigning numbers or symbols) to
elicit the attitudinal responses of subjects
toward objects, events, or persons.

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Developing Scales
 Categories of attitudinal scales:
(not to be confused with the four
different types of scales)
 The Rating Scales
 The Ranking Scales

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Developing Scales
 Rating scales have several response
categories and are used to elicit
responses with regard to the object,
event, or person studied.
 Ranking scales, make comparisons
between or among objects, events, or
persons and elicit the preferred choices
and ranking among them.

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Rating Scales
 The following rating scales are often
used in organizational research.
1. Dichotomous scale
2. Category scale
3. Likert scale
4. Numerical scale

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Rating Scales
5. Semantic differential scale
6. Itemized rating scale
7. Fixed or constant sum rating scale
8. Stapel scale
9. Graphic rating scale
10. Consensus scale

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Dichotomous Scale
 Is used to elicit a Yes or No answer.
(Note that a nominal scale is used to
elicit the response)
 Example 4
Do you own a car? Yes No

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Category Scale
 It uses multiple items to elicit a single
response.
 Example 5
Where in Jordan do you reside?
Amman
Mafraq
Irbid
Zarqa
Other

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Likert Scale
 Is designed to examine how strongly
subjects agree or disagree with
statements on a 5-point scale as
following:
_________________________________
Strongly Neither Agree Strongly
Disagree Disagree Nor Disagree Agree Agree
1 2 3 4 5
______________________________________________________

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Likert Scale
 This is an Interval scale and the
differences in responses between any
two points on the scale remain the
same.

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Semantic Differential Scale
 We use this scale when several
attributes are identified at the
extremes of the scale. For instance,
the scale would employ such terms as:
Good – Bad
Strong – Weak
Hot – Cold

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Semantic Differential Scale
 This scale is treated as an Interval
scale.
 Example 6
What is your opinion on your supervisor?
Responsive--------------Unresponsive
Beautiful-----------------Ugly
Courageous-------------Timid

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Numerical Scale
 Is similar to the semantic differential scale,
with the difference that numbers on a 5-
points or 7-points scale are provided, as
illustrated in the following example:
How pleased are you with your new job?
Extremely Extremlely
pleased 5 4 3 2 1 displeased

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Itemized Rating Scale
 A 5-point or 7-point scale is provided for each item
and the respondent states the appropriate number on
the side of each item. This uses an Interval Scale.
 Example 7(i)
Respond to each item using the scale below, and indicate your
response number on the line by each item.
1 2 3 4 5
Very unlikely unlikely neither likely very likely
unlikely nor
likely
--------------------------------------------------------------------------------
I will be changing my job in the near future. --------

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 Note that the above is balanced
rating with a neutral point.
 The unbalance rating scale which
does not have a neutral point, will be
presented in the following example.

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 Example 7(ii)
Circle the number that is closest to how you
feel for the item below:
Not at all Somewhat Moderately Very much
interested interested interested interested
1 2 3 4
--------------------------------------------------------------------------------
How would you rate your interest 1 2 3 4
In changing current organizational
Policies?

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Fixed or Constant Sum Scale
 The respondents are asked to distribute a
given number of points across various items.
 Example : In choosing a toilet soap, indicate the importance
you attach to each of the following five aspects by allotting
points for each to total 100 in all.
Fragrance -----
Color -----
Shape -----
Size -----
_________
Total points 100
This is more in the nature of an ordinal scale.

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Stapel Scale
 This scale simultaneously measures
both the direction and intensity of
the attitude toward the items under
study. The characteristic of interest
to the study is placed at the center
and a numerical scale ranging, say from
+3 to – 3, on either side of the item as
illustrated in the following example:

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Example 8: Stapel Scale
 State how you would rate your supervisor’s abilities with respect
to each of the characteristics mentioned below, by circling the
appropriate number.
+3 +3 +3
+2 +2 +2
+1 +1 +1
Adopting modern Product Interpersonal
Technology Innovation Skills
- 1 - 1 - 1
- 2 - 2 - 2
- 3 - 3 - 3

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Graphic Rating Scale
 A graphical representation helps the
respondents to indicate on this scale
their answers to a particular question
by placing a mark at the appropriate
point on the line, as in the following
example:

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Graphic Rating Scale
 Example 9
 On a scale of 1 to 10, how would you
rate your supervisor?
5
1
10

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Ranking Scales
 Are used to tap preferences between
two or among more objects or items
(ordinal in nature). However, such
ranking may not give definitive clues
to some of the answers sought.

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Ranking Scales
 Example 10
There are 4 product lines, the manager seeks
information that would help decide which product line
should get the most attention.
Assume:
35% of respondents choose the 1st product.
25% of respondents choose the 2nd product.
20% of respondents choose the 3rd product.
20% of respondents choose the 4th product.
100%

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Ranking Scales
 The manager cannot conclude that the first
product is the most preferred. Why?
 Because 65% of respondents did not choose
that product. We have to use alternative
methods like Forced Choice, Paired
Comparisons, and the Comparative Scale.
 We will describe the Forced Choice as an
example.

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Forced Choice
 The forced choice enables respondents
to rank objects relative to one another,
among the alternative provided. This is
easier for the respondents, particularly
if the number of choice to be ranked is
limited in number.

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Forced Choice
 Example 11
Rank the following newspapers that you
would like to subscribe to in the order of
preference, assigning 1 for the most
preferred choice and 5 for the least preferred.
•
‫الدستور‬
-------
•
‫الرأي‬
---------
•
‫اليوم‬ ‫أخبار‬
----
•
‫الغد‬
-----------
•
‫شيحان‬
--------

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Goodness of Measures
 It is important to make sure that the
instrument that we develop to measure
a particular concept is accurately
measuring the variable, and we are
actually measured the concept that
we set out to measure.

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 We need to assess the goodness of
the measures developed. That is, we
need to be reasonably sure that the
instruments we use in our research do
indeed measure the variables they
are supposed to, and that they
measure them accurately.

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 How can we ensure that the measures
developed are reasonably good?
 First an item analysis of the
responses to the questions tapping the
variable is done.
 Then the reliability and validity of
the measures are established.

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Item Analysis
 Item analysis is done to see if the items in
the instrument belong there or not. Each item
is examined for its ability to discriminate
between those subjects whose total scores
are high, and those with low scores.
 In item analysis, the means between the
high-score group and the low-score group
are tested to detect significant differences
through the t-values.

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Item Analysis
 The items with a high t-value are then
included in the instrument. Thereafter,
tests for the reliability of the
instrument are done and the validity
of the measure is established.

Reliability
 Reliability of measure indicates extent
to which it is without bias and hence
ensures consistent measurement across
time (stability) and across the various
items in the instrument (internal
consistency).
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Stability
 Stability: ability of a measure to remain
the same over time, despite
uncontrollable testing conditions or the
state of the respondents themselves.
 Test–Retest Reliability: The reliability
coefﬁcient obtained with a repetition of the
same measure on a second occasion.
 Parallel-Form Reliability: Responses on
two comparable sets of measures tapping
the same construct are highly correlated.
84

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Test-Retest Reliability
 When a questionnaire containing some items
that are supposed to measure a concept is
administered to a set of respondents now,
and again to the same respondents, say
several weeks to 6 months later, then the
correlation between the scores obtained is
called the test-retest coefficient.
 The higher the coefficient is, the better the
test-retest reliability, and consequently, the
stability of the measure across time.

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Parallel-Form Reliability
 When responses on two comparable
sets of measures tapping the same
construct are highly correlated, we have
parallel-form reliability.
 Both forms have similar items and the
same response format, the only
changes being the wording and the
order or sequence of the questions.

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Parallel-Form Reliability
 What we try to establish in the parallel-
form is the error variability resulting from
wording and ordering of the questions.
 If two such comparable forms are highly
correlated (say 8 and above), we may be
fairly certain that the measures are
reasonably reliable, with minimal error
variance caused by wording, ordering, or
other factors.

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Internal Consistency
 Internal Consistency of Measures is
indicative of the homogeneity of the items in the
measure that tap the construct.
 Inter-item Consistency Reliability: This is a test
of the consistency of respondents’ answers to all
the items in a measure. The most popular test of
inter-item consistency reliability is the Cronbach’s
coefficient alpha.
 Split-Half Reliability: Split-half reliability reflects
the correlations between two halves of an
instrument.

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Validity
 Validity tests show how well an instrument
that is developed measures the particular
concept it is intended to measure. Validity
is concerned with whether we measure the
right concept.
 Several types of validity tests are used to
test the goodness of measures: content
validity, criterion-related validity, and
construct validity.

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Content Validity
 Content validity ensures that the measure
includes an adequate and representative
set of items that tap the concept.
 The more the scale items represent the
domain of the concept being measured, the
greater the content validity.
 In other words, content validity is a
function of how well the dimensions and
elements of a concept have been
delineated.

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Criterion-Related Validity
 Criterion-Related Validity is established
when the measure differentiates individuals
on a criterion it is expected to predict. This
can be done by establishing what is called
concurrent validity or predictive validity.
 Concurrent validity is established when the
scale discriminates individuals who are
known to be different; that is, they should
score differently on the instrument as in the
following example.

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Criterion-Related Validity
 Example 12
If a measure of work ethic is developed and
administered to a group of welfare recipients,
the scale should differentiate those who are
enthusiastic about accepting a job and glad
of a opportunity to be off welfare, from those
who would not want to work even when
offered a job.

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Example 12 (Cont.)
 Those with high work ethic values would
not want to be on welfare and would ask for
employment. Those who are low on work
ethic values, might exploit the opportunity to
survive on welfare for as long as possible.
 If both types of individuals have the
same score on the work ethic scale, then
the test would not be a measure of work
ethic, but of something else.

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Construct Validity
 Construct Validity testifies to how well the results
obtained from the use of the measure fit the theories
around which the test is designed. This is assessed
through convergent and discriminant validity.
 Convergent validity is established when the scores
obtained with two different instruments measuring
the same concept are highly correlated.
 Discriminant validity is established when, based
on theory, two variables are predicted to be
uncorrelated, and the scores obtained by measuring
them are indeed empirically found to be so.

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 Goodness of Measures is established
through the different kinds of validity and
reliability.
 The results of any research can only be as
good as the measures that tap the concepts
in the theoretical framework.
 Table 7.2 summarizes the kinds of validity
discussed in the lecture.

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