error why do we care?. reliability degree to which measures are free from random error and,...
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Error
Why do we care?
Reliability
• Reliability• Degree to which measures are free from
random error and, therefore, provide consistent data.
• There are three ways to assess reliability• Test-retest, equivalent forms, and internal
consistency (see the next slide)
Assessing the Reliability of a Measurement Instrument
Test-retest reliability: Use the same instrument a second time under
as nearly the same conditions as possible.
Equivalent form reliability: Use two instruments that are as similar as
possible to measure the same object during the
same time period.
Internal consistency reliability: Compare different samples of items being
used to measure a phenomenon during the
same time period.
Validity
• Extent to which a measurement instrument actually measures the attribute it was intended to measure.
• Validity can be examined from a number of different perspectives, including:• Face, content, criterion-related, and construct
validity (see next slide)
Assessing the Validity of a Measurement Instrument
Face validity Researchers judge the degree to which a measurementinstrument seems to measure what it is supposed to.
Content validity The degree to which the instrument items represent the universe of the concept under study.
Criterion-related The degree to which a measurement instrument canvalidity predict a variable that is designated a criterion.
(a) Predictive ability; (b) Concurrent validity
Construct validity The degree to which a measure confirm a hypothesiscreated from a theory based upon the concepts understudy.(a) Convergent validity; (b) Discriminate validity
Illustrations of Possible Reliability and Validity
Situations in Measurement.... .....
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Situation 1 Situation 3Situation 2
Neither reliable nor Valid
Highly reliable but not valid
Highly reliable and valid
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Sample Survey BlueprintResearchQuestion orObjective
SurveyQuestion
Describe thecharacteristicsof our currentcustomerspreferredcookie?
Describe the“perfect”chocolate chipcookie.
Who is the “endconsumer” ofthe purchasedcookie?
You bring thecookies homefrom the store.Who eats them?
Measurement
The Concept of Measurement and Measurement Scales
• Measurement• Process of assigning numbers or labels to
things in accordance with specific rules to represent quantities or qualities of attributes.
• Rule: A guide, method, or command that tells a researcher what to do.
• Scale: A set of symbols or numbers constructed to be assigned by a rule to the individuals (or their behaviors or attitudes) to whom the scale is applied.
Types of Measurement Scales
• Nominal Scales• Scales that partition data into mutually
exclusive and collectively exhaustive categories.
• Ordinal Scales• Nominal scales that can order data.
• Interval Scales• Ordinal scales with equal intervals between
points to show relative amounts; may include an arbitrary zero point.
• Ratio Scales• Interval scales with a meaningful zero point so
that magnitudes can be compared arithmetically.
Nominal
Ordinal
Interval
Ratio
Win Place Show
1 length 2 lengths
40 to 1 long-shot pays $40
Type of Scale Numerical Operation
Descriptive Statistics
Nominal Counting Frequency;
Percentage; mode
Ordinal Rank ordering (plus…)Median
Range; Percentile
Interval Arithmetic operations on intervals bet numbers
(plus…) Mean;
Standard deviation;
variance
Ratio Arithmetic operations on actual quantities
(plus…) Geometric mean; Co-efficent of variation
Selecting appropriate univariate statistical method
Scale Business Problem
Statistical question to be
asked
Possible test of statistical significance
Nominal Scale
Identify sex of key executives
Is the number of female executives equal to the number of males executives?
Chi-square test
Scale Business Problem
Statistical question to be
asked
Possible test of statistical significance
Nominal Scale
Indicate percentage of key executives who are male
Is the proportion of male executives the same as the hypothesized proportion?
T-test
Scale Business Problem
Statistical question to be
asked
Possible test of statistical significance
Ordinal scale Compare actual and expected evaluations
Does the distribution of scores for a scale with categories of poor,good, excellent differ from an expected distribution?
Chi-square test
Scale Business Problem
Statistical question to be
asked
Possible test of statistical significance
Interval or Ratio scale
Compare actual and hypothetical values of average salary
Is the sample mean significantly different from the hypothesized population mean?
Z-test (sample is large)
T-test (sample is small)
Questionnaire design
A survey is only as good as the questions it asks
What should you ask?
• The questions asked are a function of previous decisions
• The questions asked are a function of future decisions (such as statistical analysis)
Key criteria
• Questionnaire relevancy• No unnecessary information is collected and
only information needed to solve the problem is obtained. Be specific about your data needs; tie each question to an objective
• Questionnaire accuracy• Information is both reliable and valid
Phrasing Questions
• Open ended response versus fixed alternative questions
“?”• Decision criteria: type of research; time;
method of delivery; budget; concerns regarding researcher bias
Avoid
• Leading questions
• Overly complex questions
• Use of jargon
• Loaded questions (can use a counterbiasing statement)
• Ambiguity
• Double barreled questions
• Making assumptions
Order?
• Order bias results from an alternative answer’s position in a set of answers or from the sequencing of questions• Funneling technique: general to specific helps
understand the frame of reference first
• Anchoring effect: the first concept measured tends to become a comparison point from which subsequent evaluations are made
Types of questions
• Single dichotomy or dichotomous-alternative questions“Are you currently registered in a course at the
University of Lethbridge?Yes____ No____”
• Respondent chooses one of two alternatives (yes/no; male/female)
• What scale would this data create?
Types of fixed alternative questions…
• Multi-choice alternative• Respondent chooses from several
alternatives
• Many types…
Types of fixed alternative questions…
• Determinant choice• Choose only one from several possible responses
“Which faculty are you currently registered in at the University of Lethbridge?
Management ___Education ____Arts/Science____Health sciences____Combined degree____
• What type of scale would these data create?
Multi-choice alternative questions…
• Frequency determination
• Asks for an answer about frequency of occurrence
In a typical week, how often do you purchase chocolate chip cookies?
__never
__ once
__ 2 or more timesWhat type of scale would these data create?
• Check list• Provide multiple answers to a single question• Should be mutually exclusive and exhaustive“What brands of chocolate chip cookies have
you, to the best of your memory, purchased in the past month (check all that apply?)”
__ Dare__ Chips A’hoy__ Presidents Choice Decadent etc. etc.
• What type of scale would these data create?
• Attitude rating scalesAttitude:
An enduring disposition to consistently respond to various aspect of the world, including persons, events and objects
Typically seen as having three components:
• Cognitive
• Affective
• Behavioural
Attitude Scales: Scaling Defined
The term scaling refers to procedures for attempting to determine quantitative measures of subjective and sometimes abstract concepts. It is
defined as a procedure for the assignment of numbers to a property of objects in order to
impart some of the characteristics of numbers to the properties in question.
Unidimensional Scaling
Multidimensional Scaling
Procedures designed to
measure only one attribute of a respondent or
object
Procedures designed to measure several dimensions of a respondent or
object
Attitude measuring process
• Ranking
• Rating
• Sorting
• Choice
Types of attitude scales
• Simple attitude scales• Most basic form – respondent responds to a single
question• Do not allow for fine distinctions or placement on
continua• You are at a company party and are feeling nervous,
but you are obligated to be there. Do you:__ find someone you know to buddy up with__ take it as an opportunity to meet new people
What type of scale would these data create?
• Category scales• More sensitive; provides more information
• Overall, how satisfied are you with the high speed performance of your Mercedes:
__ very satisfied
__ somewhat satisfied
__ neither satisfied nor dissatisfied
__ somewhat dissatisfied
__ very dissatisfied
If you could choose, how long would each term be?
___26 weeks __ 13 weeks __ 6 weeks ___4 weeks
What type of scale would these data create?
• Summated rating scales – the Likert scale• Respondents indicate their attitudes by
checking how strongly they agree or disagree with statements
• Chocolate chip cookies are my preferred variety of cookie
Strongly disagree Disagree Uncertain Agree Strongly Agree
(1) (2) (3) (4) (5)
What type of scale would these data create?
• Semantic Differential Rating scale• An attitude measure consisting of a series of
seven-point bipolar rating scales allowing response to a “concept”
Think of your favorite type of cookie. Rate it on each of the following continua:
Hard------------------------------------------------------Soft
Lots of chips---------------------------------------Fewer chips
Crispy---------------------------------------------------chewy
What type of scale would these data create?
• Numerical Rating scale• Similar to a semantic differential except that it uses
numbers as response options to identify response positions instead of verbal descriptions
Think of your favorite type of cookie. Rate it on each of the following continua:
Hard------------------------------------------------------------------------Soft
8 7 6 5 4 3 21
This scale is called an 8 point numerical scale, why?
What type of scale would these data create?
• Constant Sum Scales• Attributes based on their importance to the person.
Respondents are asked to divide a constant sum to indicate the relative importance of attributes
Example: Suppose the photocopy budget per professor was $100 per month. How much should be allocated to the following. Divide the $100 according to your preference:
____ photocopying for student needs; ____ photocopying for research needs; ____ photocopying for committee needs.====$100 TOTAL
• Stapel Scales• An attitude measure that places a single adjective in the
center of an even-number range of numerical values
Example:Research Methodology
+3+2+1
Exciting-1-2-3
• Graphic Rating Scales• An attitude measure consisting of a graphic
continuum that allows respondents to rate an object by choosing any point on the continuum
• Rank-Order Scales• Scales in which the respondent compares one
item with another or a group of items against each other and ranks them.
Example: handout
Most important skills• Adaptability to change• Problem identification• Listening skills• Written communication• Leadership• Informal Oral communication• Analytical thinking/problem solving• Time management• Coping with stress/job pressures• Interpersonal relations• Formal oral presentations
Most important skillsAdaptability to changeProblem identificationListening skillsWritten communicationLeadershipInformal Oral communicationAnalytical thinking/problem solvingTime managementCoping with stress/job pressuresInterpersonal relationsFormal oral presentations
8 96 61 12 44 23 35 57 1011 79 810 11
Managers
Business
grads
• Paired Comparison Scales• Respondent is presented with two objects and is
asked to pick the preferred.
Example: Which type of cookie do you prefer
__ chocolate chip
__ oatmeal
__ I do not have a preference between these two
• Sorting• Respondent indicates their attitudes or beliefs
by arranging items.
Example: Please sort the following cards with pictures of cookies into the following categories
Like
Dislike
Neither like nor dislike
• Ranking, sorting, rating or choice?
• How many categories or response positions?
• Balanced or unbalanced?
• Forced choice or nonforced choice?
• Single measure or index?
Decisions