Methodology

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Chapter Nine
The Concept of Measurement
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Chapter Nine The Concept of Measurement

• Understand the concept of measurement
• Learn about the measurement process and how to
  develop a good measurement scale
• Understand the four levels of scales and their
  typical usage
• Explore the concepts of reliability and validity

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Measurement Process
Measurement

• The Process of assigning numbers or labels to
  persons, objects, or events in accordance with
  specific rules for representing quantities or
  qualities or attributes.

• The guide, method, or command that tells a
  researcher what to do.

Rule
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Data Types
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Nominal Data
Scales that partition data into mutually
exclusive and collectively exhaustive categories.

• Classification Type Data
• Yes or no questions
• Nouns in general
• Gender
• Race / Ethnicity
• Occupation
• Text open-ended questions.
• Analysis Approach
• Cross tabulations / Percentages
• Sums and frequency counts
• One cant tell the relative value of responses.

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Ordinal Data
Scales that maintain the labeling characteristics
of nominal scales and have the ability to order
data.

• Ranking Type Data
• Best liked, worst liked
• Win, place, or show
• First, second, third
• Small, medium, and large
• Comparisons rankings -
• rank these movies from best to worst
• Analysis Approach
• Cross tabulations, sums and frequency counts
• Percentages, mode, mean for some types
• One can tell the relative order of responses
• but not the distance between responses

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Interval Data
Scales that have the characteristics of ordinal
scales, plus equal intervals between points.

• Comparison Type Data
• One a 1 to 10 scale
• Age, income, etc. as ranges
• Red, blue, green
• - if each rated from 1 to X
• Analysis Approach
• Standard deviation, variance, kurtosis
• Descriptive statistics - mean, median, mode
• Sums and ranged frequency counts
• Correlation
• Can tell the relative value of responses and
• can tell the distance between responses.

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Ratio Data
Scales that have the characteristics of interval,
plus a meaningful zero point.

• Flat Numeric Type Data
• Age 50 (not an age range)
• Income 25,000 (not an income range)
• Number of children ________
• Analysis Approach
• Standard deviation, variance, kurtosis
• Descriptive statistics - mean, median, mode
• Sums and ranged frequency counts
• Pearson correlation, regression
• Can tell the relative value of responses and
• can tell the distance between responses and
• how they relate to zero.

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Reliability and Validity
Reliability Degree to which measures are free
from random error and, therefore, provide
consistent data. The extent to which the survey
responses are internally consistent. Validity
Degree to which what the researcher was trying to
measure was actually measured.
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Testing Reliability

• Test and Retest
• The ability of the same instrument to produce
  consistent results when used a second time under
  conditions as similar as possible to the original
  conditions.
• Stability
• Lack of change in results from test to test.
• Equivalent Form
• When two very similar forms of an instrument
  produce closely correlated results.

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Testing Reliability

• Internal Consistency
• The ability of an instrument to produce similar
  results when used on different samples during the
  same time period to measure a phenomenon.
• Spilt Half
• A method of assessing the reliability of a scale
  by dividing the total set of measurement items in
  half and correlating the results.

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Testing Validity

• Face
• The degree to which a measurement seems to
  measure what it is supposed to measure.
• Content
• The representativeness, or sampling adequacy, of
  the content of the measurement instrument.

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Testing Validity

• Criterion Related
• The degree to which a measurement instrument can
  predict a variable that is designated a
  criterion.
• Construct
• The degree to which a measurement instrument
  represents and logically connects, via the
  underlying theory, the observed phenomenon to the
  construct.

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Testing Validity

• Convergent
• The degree of correlation among different
  measures that purport to measure the same
  construct.
• Discriminate
• The measure of the lack of association among
  constructs that are supposed to be different..

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Testing Validity

• Predictive
• The degree to which a future level of a
  criterion can be forecast by a current
  measurement scale.
• Concurrent
• The degree to which another variable, measured
  at the same point in time as the variable of
  interest, can be predicted by the measurement
  instrument.

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Reliability and Validity

• Neither Reliable nor Valid

• Highly Reliable but not Valid

• Highly Reliable and Valid

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Measurement Scales
Procedures for assigning numbers or symbols to
properties of an object in order to impart some
numerical characteristics to the properties in
question.

• Scaling
• Defined

• Unidimensional
• Measures only one dimension of a concept,
  respondent, or object.
• Multidimensional
• Measures several dimensions of a concept,
  respondent, or object.

• Scaling
• Approaches

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Measurement Scales
Enduring organization of motivational,
emotional, perceptual, and cognitive processes
with respect to some aspect of a persons
environment.

• Attitude
• Defined

• Graphic Rating Scale

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Measurement Scales

• Itemized
• Rating
• Scale

• Non-comparative Scale
• Scales in which judgement is made without
  reference to another object, concept, or person.
• Comparative Scale
• Scales in which one object, concepts, or person
  is compared with another on a scale.

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Measurement Scales

• Uses Comparative Scaling
• Put these fast food chains in order of
  preference
• McDonalds
• Burger King
• Taco Bell

• Rank
• Order
• Scale

• Q-Sorting

Measurement scale employing a sophisticated form
of rank ordering using card sorts. Respondents
each rank X number of items in order from best to
worst by putting the cards representing the idea
at hand into ranked piles. Then the piles with
the most become the top choices. The procedure
can be done many times to winnow down the choice
to a top two or three.
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Measurement Scales
___Coke

• Paired
• Comparison

___Pepsi
Which drink do you prefer
___Coke
___Sprite
___Pepsi
___Sprite
What features do you want in a car? Sun roof
______ Leather ______ ABS Breaks
______ CD Player ______ Total 100
points

• Constant
• Sum Scale

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Measurement Scales

• Semantic
• Differential
• Scale

-5 -4 -3 -2 -1 High Value 1 2 3 4 5

• Staple
• Scale

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Measurement Scales

• Likert
• Scale

• Multiple
• Choice
• Scale

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Selecting a Scale Things to Consider

• The nature of the construct being measured
• The value and pitfalls of open ended questions
• Balanced Vs. Non-balanced
• Balanced - Scales that have the same number of
  positive and negative categories.
• Non-balanced - Scales that are weighted toward
  one end or the other of the scale.
• Forced Vs. Non-forced.
• Having an odd Vs. even number of response
  choices.

Chapter 9