error why do we care?. reliability degree to which measures are free from random error and,...

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