Copyright © 2008 by Nelson, a division of Thomson Canada Limited Chapter 11 Part 3 Measurement Concepts MEASUREMENT

LEARNING 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 description of how it will be measuredA precise definition of the concept may require a description of how it will be measured Frequently there is more than one way to measure a particular conceptFrequently there is more than one way to measure a particular concept True measurement of concepts requires a process of assigning scores or numbers to the attributes of people or objects.True measurement of concepts requires a process of assigning scores or numbers to the attributes of people or objects. The question becomes “On what basis will numbers or scores be assigned to the concept?”The question becomes “On what basis will numbers or scores be assigned to the concept?” What Is To Be Measured? Copyright © 2008 by Nelson, a division of Thomson Canada Limited 11–2

ConceptsConcepts  A generalized idea about a class of objects, attributes, occurrences, or processes Operational DefinitionsOperational Definitions  An 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) 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 Measurement Copyright © 2008 by Nelson, a division of Thomson Canada Limited 11–4

ScaleScale  Any 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 Scale  A scale in which the numbers or letters assigned to objects serve as labels for identification or classification Ordinal ScaleOrdinal Scale  A scale that arranges objects or alternatives according to their magnitude in an ordered relationship Types of Scales Copyright © 2008 by Nelson, a division of Thomson Canada Limited 11–5

Interval ScaleInterval Scale  A scale that both arranges objects according to their magnitudes and distinguishes this ordered arrangement in units of equal intervals Ratio ScaleRatio Scale  A 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) 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) Copyright © 2008 by Nelson, a division of Thomson Canada Limited 11–8 Type of ScaleNumerical OperationsDescriptive Statistics. Nominal Counting Frequency in each category Percentage in each category Mode Ordinal Rank Ordering Median Range Percentile ranking Interval Arithmetic operationsMean that preserve order andStandard deviation relative magnitudes Variance Ratio Arithmetic operationsGeometric 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 Measures Copyright © 2008 by Nelson, a division of Thomson Canada Limited 11–9

ReliabilityReliability  The degree to which measures are free from random error and therefore yield consistent results  Test-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 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) Copyright © 2008 by Nelson, a division of Thomson Canada Limited 11–11

ValidityValidity  The ability of a scale to measure what was intended to be measured  Establishing 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) 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) Copyright © 2008 by Nelson, a division of Thomson Canada Limited 11–13

SensitivitySensitivity  A measurement instrument’s ability to accurately measure variability in stimuli or responses Three Criteria For Good Measurement (cont’d) Copyright © 2008 by Nelson, a division of Thomson Canada Limited 11–14