Transcript NOMINAL SCALE

Collecting Data by
Communication
Chapter 12
Measurement
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“rules for assigning numbers to objects in such a
way as to represent quantities of attributes”
Marketers are interested in measuring many
attributes that most people rarely think in terms of
numbers.
There are four types of scales used to measure
attributes of objects:
Scales of Measurement
Ratio
Interval
Ordinal
Nominal
Higher levels of measurement have all the
properties of lower levels of measurement.
NOMINAL SCALE: measurement in which numbers are
assigned to objects solely for the purpose of
identification
Basic
Comparisons
Identity
Examples
Measures of
Average
male-female
mode (the
most frequently
occurring category)
user-nonuser
occupations
Which of the following soft drinks do you like? Check all that apply.
•Coca-Cola •Mountain Dew
Seven Up
Dr. Pepper
•Pepsi
Sprite
Ordinal Scale: measurement in which numbers are
assigned to data on the basis of some order (more than,
greater than) of the objects
Basic
Comparisons
Order
Examples
Measures of
Average
brand preference
median
social class
hardness of minerals
lumber quality grades
Rank the following soft drinks from 1 (least liked) to 6 (most
liked):
___Coca-Cola ___Mountain Dew
___Seven Up
___Dr. Pepper ___Pepsi
___Sprite
Interval Scale: measurement in which the assigned
numbers allow the comparison of the size of the
differences among and between numbers
Basic
Comparisons
Comparison
of intervals
Examples
temperature
grade point avg.
brand attitude
company image
What is your overall opinion about each of these brands?
Coca-Cola
Dr. Pepper
Pepsi
Sprite
Measures of
Average
unfavorable
1 2 3
1 2 3
1 2 3
1 2 3
4
4
4
4
favorable
5 6 7
5 6 7
5 6 7
5 6 7
mean
Ratio Scale: measurement that has a natural, or absolute, zero and
therefore allows the comparison of absolute magnitudes of the
numbers. Zero means that none of the property being measured
exists.
Basic
Comparisons
Comparison
of absolute
magnitudes
Examples
Measures of
Average
units sold
# of purchases
age
income
geometric
mean
Divide 100 points among these soft drinks according to your
likelihood of purchasing each within the next week:
___Coca-Cola ___Mountain Dew
___Seven Up
___Dr. Pepper ___Pepsi
___Sprite
Methods for Assessing Attitude
Observation of Behavior
Indirect Techniques (projective
methods)
Performance of Objective Tasks
Physiological Reactions
(Voice-pitch, galvanic skin
response)
Self-Report Techniques
A
Measuring Attitudes and Other
Unobservable Concepts
• Three General Types of Self-Report
Attitude Scales (A method of assessing
attitudes in which individuals are asked directly
for their beliefs about or feelings toward an object
or class of objects)
1. Itemized-Ratings Scales
2. Graphic-Ratings Scales
3. Comparative-Ratings Scales
1. Itemized-Ratings Scales
Summated Ratings (Likert) Scale
• A self-report technique for attitude
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measurement in which the subjects are
asked to indicate their degree of agreement
or disagreement with each of a number of
statements.
An individual’s attitude score is the total
obtained by summing (or averaging) over the
items in the scale.
Example of Likert (Summated-Ratings)
Scale
Strongly
Disagree Disagree
The celebrity
endorser is
trustworthy.
The celebrity
endorser is
unattractive.
The celebrity
endorser is an
expert on the
product.
The celebrity
endorser is not
knowledgeable
about the
product.
Neither
Agree nor
Disagree Agree
Strongly
Agree
Example of Itemized Rating Scale
Please evaluate each of the following attributes of compact
disc players according to how important the attribute is to
you personally by checking the appropriate box.
Not
Somewhat
Fairly
Extremely
Important Important Important Important
1.
Sound Quality
2.
Physical Size
3.
Brand Name
4.
Durability
Itemized-Ratings Scales
Semantic-Differential Scale
• A self-report technique for attitude
measurement in which respondents
are asked to check which cell
between a set of bipolar adjectives
or phrases best describes their
feelings toward the object.
Example of Semantic-Differential
Scale
Le Bron – Nike
Tiger Woods – Nike
Trustworthy
:
:
:
:
:
:
Not
Trustworthy
Attractive
:
:
:
:
:
:
Unattractive
:
:
:
:
:
:
Not Expert
:
Not
Knowledgeable
Expert
Knowledgeable
:
:
:
:
:
Semantic Differential Scale
LeBron
Tiger Woods
x
Trustworthy
x
Attractive
x
Expert
Knowledgeable
o
x
o
o
Not
Trustworthy
Unattractive
Not Expert
o
Not
Knowledgeable
2. Graphic rating scales
Raters indicate their rating by
placing a check at the appropriate
point on a line that runs from one
extreme of the attribute to the other
The score is assessed by measuring
the length of the line from one end
to the marked position
Example of Graphic Rating Scale
Please evaluate each of the following attributes of compact
disc players according to how important the attribute is to
you personally by placing an “X” at the position on the
horizontal line that most accurately reflects your feelings.
Attribute
1.
Sound Quality
2.
Physical Size
3.
Brand Name
4.
Durability
Not Important
Important
Comparative Rating Scale
Respondents are asked to judge
each attribute with direct reference
to the other attributes being
evaluated
Comparative Rating Scale
Please divide 100 points between the following attributes of
compact disc players according to the relative importance
of each attribute to you.
Sound Quality
Physical Size
Brand Name
Durability
100
points
Interpreting Rating Scales:
Raw Scores vs. Norms
• A service provider received an
average score of 5.13 on a 1-7
service quality scale, where 1 =
“much less than I expected” and 7 =
“much more than I expected.”
•
Is this score good or bad?
Interpreting Rating Scales:
Raw Scores vs. Norms
• Would your answer change if you knew
that 75% of similar service providers
posted higher scores than 5.13?
• It is very difficult to interpret a rating
scale score using only the score itself
and the scale on which it was obtained
to provide meaning. A comparative
standard, or norm, is needed.
Interpreting Rating Scales:
Raw Scores vs. Norms
Population-based norms give meaning to
scores by comparing them to scores
obtained by similar entities
Time-based norms track scores for an
entity over time and they are useful for
tracking progress and identifying
problem area
Other Considerations in Designing Scales
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Reverse Scaling
Response set bias when respondents begin to answer all the
questions in a similar way due to boredom or lack of attention
• Number of Items in a Scale
If an overall summary judgment is needed: global measure
If more information about how various aspects of the phenomenon
are viewed by respondents: composite measures
More items are better than fewer items
• Number of Scale Positions
Scales with 5-9 positions are used routinely in marketing research
• Including a “Don’t Know” Category
Use when high percentage of respondents are likely not to have
encountered or thought about the object or issue in the study
• Determining Which Type of Scale to Use
Let common sense guide your choice. Some cultures may not be
familiar with these scales.
Establishing the Validity and Reliability of
Measures
SYSTEMATIC ERROR
Error in measurement that is also known as
constant error since it affects the measurement in
a constant way.
RANDOM ERROR
Error in measurement due to temporary aspects
of the person or measurement situation that
affects the measurement in irregular ways.
RANDOM
ERROR
SYSTEMATIC
ERROR
RELIABILITY
Ability of a measure to obtain similar scores for the
same object, trait, or construct across time, across
different evaluators, or across the items forming the
measure.
VALIDITY
The extent to which differences in scores on a
measuring instrument reflect true differences among
individuals, groups, or situations in the characteristic
that it seeks to measure or true differences in the same
individual, group, or situation from one occasion to
another, rather than systematic or random errors.
Unreliable
Not Valid
Reliable
Not Valid
Reliable
Valid
A measure can be reliable but not
valid.
A valid measure must be reliable.