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Copyright © 2008 by Nelson, a division of Thomson Canada Limited
Chapter
11
Part 3
Measurement Concepts
MEASUREMENT
LEARNING OBJECTIVESLEARNING OBJECTIVESLEARNING OBJECTIVESLEARNING OBJECTIVES
1. To know how a researcher might answer the question “What is to be measured?”
2. To define the term operational definition
3. To distinguish among nominal, ordinal, interval, and ratio scales
4. To understand the need for index or composite measures
5. To define the three criteria for good measurement
6. To discuss the various methods for determining reliability
7. To discuss the various methods for assessing validity
What you will learn in this chapter
Copyright © 2008 by Nelson, a division of Thomson Canada Limited 11–1
• A precise definition of the concept may require A precise definition of the concept may require a description of how it will be measureda description of how it will be measured
• Frequently there is more than one way to Frequently there is more than one way to measure a particular conceptmeasure a particular concept
• True measurement of concepts requires a True measurement of concepts requires a process of assigning scores or numbers to the process of assigning scores or numbers to the attributes of people or objects.attributes of people or objects.
• The question becomes “On what basis will The question becomes “On what basis will numbers or scores be assigned to the numbers or scores be assigned to the concept?”concept?”
What Is To Be Measured?What Is To Be Measured?What Is To Be Measured?What Is To Be Measured?
Copyright © 2008 by Nelson, a division of Thomson Canada Limited 11–2
• ConceptsConceptsA generalized idea about a class of objects,
attributes, occurrences, or processes
• Operational DefinitionsOperational DefinitionsAn explanation that gives meaning to a concept by
specifying the activities or operations necessary to measure it
Conceptual definition A verbal explanation of the meaning of a concept. It defines
what the concept is and what it is not
What Is To Be Measured? (cont’d)What Is To Be Measured? (cont’d)What Is To Be Measured? (cont’d)What Is To Be Measured? (cont’d)
Copyright © 2008 by Nelson, a division of Thomson Canada Limited 11–3
• Measurement RuleMeasurement Rule Example: “Assign the numerals 1 through 7 to
individuals according to how brand loyal they are. If the individual is extremely brand loyal, assign a 7. If the individual is a total brand switcher with no brand loyalty, assign the numeral 1.”
Rules of MeasurementRules of MeasurementRules of MeasurementRules of Measurement
Copyright © 2008 by Nelson, a division of Thomson Canada Limited 11–4
• ScaleScaleAny series of items that are arranged progressively
according to value or magnitude; a series into which an item can be placed according to its quantification
• Nominal ScaleNominal ScaleA scale in which the numbers or letters assigned to
objects serve as labels for identification or classification
• Ordinal ScaleOrdinal ScaleA scale that arranges objects or alternatives
according to their magnitude in an ordered relationship
Types of ScalesTypes of ScalesTypes of ScalesTypes of Scales
Copyright © 2008 by Nelson, a division of Thomson Canada Limited 11–5
• Interval ScaleInterval ScaleA scale that both arranges objects according to their
magnitudes and distinguishes this ordered arrangement in units of equal intervals
• Ratio ScaleRatio ScaleA scale that has absolute rather than relative
quantities and an absolute zero where there is an absence of a given attribute
Types of Scales (cont’d)Types of Scales (cont’d)Types of Scales (cont’d)Types of Scales (cont’d)
Copyright © 2008 by Nelson, a division of Thomson Canada Limited 11–6
• Mathematical and Statistical Analysis of ScalesMathematical and Statistical Analysis of Scales
Types of Scales (cont’d)Types of Scales (cont’d)Types of Scales (cont’d)Types of Scales (cont’d)
Copyright © 2008 by Nelson, a division of Thomson Canada Limited 11–8
Type of Scale Numerical Operations Descriptive Statistics . Nominal Counting Frequency in each category
Percentage in each category Mode
Ordinal Rank Ordering Median Range Percentile ranking
Interval Arithmetic operations Mean that preserve order and Standard deviation relative magnitudes Variance
Ratio Arithmetic operations Geometric mean on actual quantities Coefficient of variation
Attribute A single characteristic or fundamental feature of an object,
person, situation, or issue
Index (or composite) measure A composite measure of several variables used to measure
a single concept; a multi-item instrument
Index MeasuresIndex MeasuresIndex MeasuresIndex Measures
Copyright © 2008 by Nelson, a division of Thomson Canada Limited 11–9
• ReliabilityReliabilityThe degree to which measures are free from random
error and therefore yield consistent resultsTest-retest method
Administering the same scale or measure to the same respondents at two separate points in time to test for stability
Split-half method A method for assessing internal consistency by checking
the results of one-half of a set of scaled items against the results from the other half
Three Criteria For Good MeasurementThree Criteria For Good MeasurementThree Criteria For Good MeasurementThree Criteria For Good Measurement
Copyright © 2008 by Nelson, a division of Thomson Canada Limited 11–10
• Reliability (cont’d)Reliability (cont’d)Equivalent-form method
A method that measures the correlation between alternative instruments, designed to be as equivalent as possible, administered to the same group of subjects
Three Criteria For Good Measurement (cont’d)Three Criteria For Good Measurement (cont’d)Three Criteria For Good Measurement (cont’d)Three Criteria For Good Measurement (cont’d)
Copyright © 2008 by Nelson, a division of Thomson Canada Limited 11–11
• ValidityValidityThe ability of a scale to measure what was intended
to be measuredEstablishing validity
Face (or content) validity: Professional agreement that a scale’s content logically appears to accurately reflect what was intended to be measured
Criterion validity: The ability of a measure to correlate with other standard measures of the same construct or established criterion
Construct validity: The ability of a measure to provide empirical evidence consistent with a theory based on the concepts
Three Criteria For Good Measurement (cont’d)Three Criteria For Good Measurement (cont’d)Three Criteria For Good Measurement (cont’d)Three Criteria For Good Measurement (cont’d)
Copyright © 2008 by Nelson, a division of Thomson Canada Limited 11–12
• Reliability versus ValidityReliability versus Validity– Reliability, although necessary for validity, is not
sufficient by itself Example: Exhibit 11.5
Three Criteria For Good Measurement (cont’d)Three Criteria For Good Measurement (cont’d)Three Criteria For Good Measurement (cont’d)Three Criteria For Good Measurement (cont’d)
Copyright © 2008 by Nelson, a division of Thomson Canada Limited 11–13
• SensitivitySensitivityA measurement instrument’s ability to accurately
measure variability in stimuli or responses
Three Criteria For Good Measurement (cont’d)Three Criteria For Good Measurement (cont’d)Three Criteria For Good Measurement (cont’d)Three Criteria For Good Measurement (cont’d)
Copyright © 2008 by Nelson, a division of Thomson Canada Limited 11–14