Chapter 7 Measurement Scaling, Reliability, Validity

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1

Measur

ement:

Scaling,

Reliability, Validity

CHAPTER 7 CHAPTER 7

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Scale



 Is a tl r mec!anism by "!ic!Is a tl r mec!anism by "!ic!

indi#iduals are distinguis!ed as t indi#iduals are distinguis!ed as t !" t!ey di$er %rm ne ant!er !" t!ey di$er %rm ne ant!er n t!e #ariables % interest t ur n t!e #ariables % interest t ur study&

study&

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Scale



 Is a tl r mec!anism by "!ic!Is a tl r mec!anism by "!ic!

indi#iduals are distinguis!ed as t indi#iduals are distinguis!ed as t !" t!ey di$er %rm ne ant!er !" t!ey di$er %rm ne ant!er n t!e #ariables % interest t ur n t!e #ariables % interest t ur study&

study&

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scales



 T!ere are T!ere are fourfour basic ty(es % basic ty(es %

scales: scales: 1&

1& )minal Scale)minal Scale

*&

*& +rdinal Scale+rdinal Scale

'&

'& Inter#al ScaleInter#al Scale

&

& Rati ScaleRati Scale

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)minal Scale

 A nominal scale is ne t!at all"s t!e researc!er t

assign sub-ects t certain categries r gru(s&

 .!at is yur de(artment/

+ Mar0eting + Maintenance + inance

+ Prductin + Ser#icing + Persnnel + Sales + Public Relatins + Accunting

 .!at is yur gender/

+ Male + emale

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)minal Scale

 T!e information t!at can be

generated %rm nominal scaling

is t calculate t!e (ercentage 2r

%re3uency4 % males and %emales in ur sam(le % res(ndents&

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E6am(le 1

 Nominally scale t!e natinality % indi#iduals in

a gru( % turists t a cuntry during a certain year&

 .e culd nminally scale t!is #ariable in t!e

%ll"ing mutually exclusive and collectively exhaustive categories& American a(anese Russian Malaysian C!inese 8erman Arabian +t!er 9

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E6am(le 1

 )te t!at e#ery res(ndent !as t t int ne % t!e ab#e categries and t!at t!e scale "ill all"

cm(utatin % t!e numbers and

percentages % res(ndents t!at t int t!em&

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+rdinal Scale

 Ordinal scale: nt nly categri;es #ariables in suc! a "ay as t dente di$erences amng

#arius categries, it als ran0<rders categries in sme meaning%ul "ay&

 .!at is t!e !ig!est le#el % educatin yu !a#e cm(leted/

+ =ess t!an Hig! Sc!l

+ Hig! Sc!l>8E? E3ui#alent + Cllege ?egree

+ Masters ?egree + ?ctral ?egree

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+rdinal Scale

 T!e (re%erence "uld be ran0ed 2 %rm best t "rse r %rm rst t last4 and numbered as 1, *, ', and s n&

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E6am(le *

 Ran0 t!e %ll"ing #e

characteristics in a job in terms % !" im(rtant t!ey are %r yu& u should rank t!e mst

im(rtant item as 1, t!e ne6t in im(rtance a *, and s n, until

yu !a#e ran0ed eac! % t!em 1, *, ', , r 5&

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E6am(le * 2Cnt&4

 Job Characteristic

Ranking

T!e ((rtunity (r#ided by t!e -b t:

1& Interacts "it! t!ers  *& Fse di$erent s0ills  '& Cm(lete a tas0 t t!e end  & Ser#e t!ers  5& .r0 inde(endently 

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E6am(le * 2Cnt&4

 T!is scale !el(s t!e researc!er t

determine the percentage %

res(ndents "! cnsider interactin "it! t!ers as mst im(rtant, t!se "! cnsider using a number % s0ills as mst im(rtant, and s n& Suc!

0n"ledge mig!t !el( in designing -bs t!at "uld be seen as mst enric!ed

by t!e ma-rity % t!e em(lyees&

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E6am(le * 2Cnt&4

 .e can see t!at t!e ordinal scale

(r#ides mre in%rmatin t!an t!e nminal scale& E#en t!ug!

di$erences in t!e ran0ing % b-ects,

(ersns are clearly 0n"n, we do

not know their magnitude.

 T!is deciency is #ercme by

interval scaling.

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1

Inter#al Scale

 nterval scale: "!ereas t!e nminal scale all"s us nly t 3ualitati#ely

distinguis! gru(s by categri;ing t!em int mutually e6clusi#e and

cllecti#ely e6!austi#e sets, and t!e rdinal scale t ran0<rder t!e

(re%erences, t!e interval scale lets us measure t!e distance bet"een any t" (ints n t!e scale& 2Standard

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Inter#al scale

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E6am(le 'a

 Indicate t!e e6tent t "!ic! yu

agree "it! t!e %ll"ing statements as t!ey relate t yur -b, by circling t!e a((r(riate number against eac!,

using the scale given below.

strngly disagree 1, ?isagree * )eit!er Agree )r ?isagree '

Agree , Strngly Agree 5&

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E6am(le 'a 2Cnt&4

 T!e %ll"ing ((rtunities $ered by t!e -b are #ery im(rtant t

me: 17 Interacting "it! t!ers 1 2 3 4 5 Fsing a number % di$erent s0ills 1 2 3 4 5 Cm(leting a tas0 %rm beginning t end 1 2 3 4 5 Ser#ing t!ers 1 2 3 4 5 .r0ing 1 2 3 4 5

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E6am(le 'a 2Cnt&4

 Su((se t!at t!e em(lyees circle t!e

numbers ', 1, *, , and 5 %r t!e #e items&

 T!e magnitude of di!erence re(resented

by t!e space bet"een (ints 1 and * n

t!e scale is the same as t!e magnitude % di$erence re(resented by t!e s(ace

bet"een (ints  and 5, r bet"een any

t!er t" (ints& Any number can be added t r subtracted %rm t!e numbers n t!e scale, still retaining t!e magnitude % t!e di$erence&

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1B

=i0ert Scale

 T!is is an nterval scale and t!e di$erences in res(nses bet"een any t" (ints n t!e scale remain t!e same&

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*D

=i0ert Scale

 Is designed t e6amine !" strngly

sub-ects agree r disagree "it! statements n a 5<(int scale as %ll"ing:



Strngly )eit!er Agree Strngly ?isagree ?isagree )r ?isagree Agree Agree

1 * '  5

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Rati Scale

 Ratio scale: #ercmes t!e

disad#antage % t!e arbitrary rigin (int % t!e inter#al scale, in t!at it !as an

abslute 2in cntrast t an arbitrary4 ;er (int, "!ic! is a meaning%ul

measurement (int&

 .!at is yur age/

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Rati Scale

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Rati Scale

 T!e ratio scale is t!e most

powerful % t!e %ur scales

because it !as a

uni"ue #ero

origin

2 nt an arbitrary rigin4&

 T!e di$erences bet"een scales are summari;ed in t!e ne6t igure&

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T!e di$erences bet"een

scales

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8dness % Measures

 It is im(rtant t ma0e sure t!at t!e instrument t!at "e de#el( t measure a (articular cnce(t is

accurately measuring t!e #ariable, and "e are actually

measured the concept t!at "e set ut t measure&

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*9

8dness % Measures

 H" can "e ensure t!at t!e

measures de#el(ed are reasnably gd/

 irst an item analysis % t!e

res(nses t t!e 3uestins ta((ing t!e #ariable is dne&

 T!en t!e reliability and validity % t!e measures are establis!ed&

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Item Analysis

 tem analysis is dne t see i% t!e items in

t!e instrument belng t!ere r nt& Eac! item is e6amined %r its ability t

discriminate bet"een t!se sub-ects "!se ttal scres are !ig!, and t!se "it! l"

scres&

 In item analysis, t!e means bet"een t!e

!ig!<scre gru( and t!e l"<scre gru( are tested t detect signicant di$erences t!rug! t!e t<#alues&

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*@

Item Analysis

 T!e items "it! a !ig! t<#alue are t!en included in t!e instrument&

T!erea%ter, tests %r t!e reliability

% t!e instrument are dne and t!e

validity % t!e measure is establis!ed&

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Reliability

 Reliability % measure indicates e6tent t "!ic! it is "it!ut bias and !ence ensures cnsistent

measurement acrss time

2stability4 and acrss t!e #arius items in t!e instrument 2internal cnsistency4&

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'D

Stability

 Stability: ability % a measure t remain t!e same #er time,

des(ite uncntrllable testing cnditins r t!e state % t!e res(ndents t!emsel#es&

@

 $est%Retest Reliability_: T!e

reliability ce%cient btained "it! a re(etitin % t!e same measure n a secnd ccasin&

 &arallel'(orm Reliability: Res(nses

n t" cm(arable sets % measures ta((ing t!e same cnstruct are !ig!ly

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'1

Validity

 )alidity tests s!" !" "ell an

instrument t!at is de#el(ed measures

t!e particular concept it is intended

t measure& )alidity is cncerned "it! "!et!er "e measure t!e rig!t cnce(t&

 *everal types of validity tests are

used t test t!e gdness % measures:

content validity+ criterion'related validity+ and construct validity&

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'*

Cntent Validity

 Content validity ensures t!at t!e measure

includes an ade"uate and representative set % items t!at ta( t!e concept.

 T!e mre t!e scale items re(resent t!e

dmain % t!e cnce(t being measured, t!e greater t!e cntent #alidity&

 In t!er "rds, content validity is a

%unctin % how well t!e dimensions and elements % a cnce(t !a#e been

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''

Criterin<Related Validity

 Criterion'Related )alidity is establis!ed

"!en t!e measure di$erentiates indi#iduals n a criterin it is e6(ected t (redict& T!is can be dne by establis!ing "!at is called concurrent validity r predictive

validity&

 Concurrent validity is establis!ed "!en

t!e scale discriminates individuals "! are 0n"n t be di$erent t!at is, t!ey

s!uld scre di$erently n t!e instrument as in t!e %ll"ing e6am(le&

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'

Criterin<Related Validity

 E6am(le 1*

I% a measure % work ethic is

de#el(ed and administered t a gru( % "el%are reci(ients, t!e scale s!uld di$erentiate t!se "! are interested abut acce(ting a -b and glad % a

((rtunity t be $ "el%are, %rm t!se "! "uld nt "ant t "r0 e#en "!en $ered a -b&

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E6am(le 1* 2Cnt&4

 T!se "it! high work values "uld nt

"ant t be n "el%are and "uld as0 %r em(lyment& T!se "! are l" n "r0 #alues, mig!t e6(lit t!e ((rtunity t sur#i#e n "el%are %r as lng as (ssible&

 I% both types of individuals !a#e t!e

same score n t!e "r0 #alues scale,

t!en t!e test "uld not be a measure % "r0 #alues , but % smet!ing else&