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Lecture 3

Social Research Methods

MMKT, MHA & MHRM

June, 2014

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Reliabilit & !aliditResearch Stud "esi#ns

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Reliabilit & !alidit

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Reliabilit

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Reliabilit

$oncerned %ith either the results o researchstud are re'eatable, hence are stable(

Also called ) Re'eatabilit *recision

+a-'le) ./ leels is not a reliable -easure $han#e in ./ leels is obsered in ca-e set o

students under dierent conditions

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Reliabilit T'es

Inter-Rater or Inter-Observer Reliability

sed to assess the de#ree to %hich dierentratersobserers #ie consistent esti-ateso the sa-e 'heno-enon(

Test-Retest Reliability

sed to assess the consistenc o a-easure ro- one ti-e to another(

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Reliabilit T'es

.nter5Rater & Test5Retest Reliabilit

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!alidit

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!alidit

$oncerned %ith the inte#rit o the conclusions

1(Measure-ent alidit

2(.nternal alidit

3(+ternal alidit

4(+colo#ical alidit

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Measure-ent alidit

Also called constructalidit

6hether a -easure is doin# the 7ob it is su''osed

to do(

+a-'le "oes ./ reall -easures the ariations in intelli#ence 8

.t 'resu''oses that a -easure is reliable(

An unreliable, unstable -easure cannot be alid(

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.nternal !alidit

Related to issue o $ausalit

Soundness o 9ndin#s that s'eci a causal

connection

+a-'le

. it is su##ested that : causes ;, then is theresearcher sure that : is causin# ;, or that

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.nternal !alidit

+a-'le 2

Reli#ious eniron-ent Reli#ious belies

"e'endent ariable 8

.nde'endent ariable 8

Ho% can %e be sure that it is the inde'endentariable res'onsible or the chan#e in de'endentariable(

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+ternal !alidit

=enerali>ation

=ender recclin# res'onsibilities

Stud done in one to%n in K(

6hether or not results are a''licable to other

to%ns

$once't o sa-'lin# 'rocedures that -ai-i>e theo''ortunit or #eneratin# re'resentatie sa-'les

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+colo#ical alidit

Social 9ndin#s are a''licable to 'eo'le

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Research Stud "esi#ns$ross5sectional Stud "esi#n

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Snon-s

.nstantaneous stud

*realence stud

Si-ultaneous stud

$ross5sectional stud

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$ross5sectional "esi#n

.dentiin# a de9ned 'o'ulation at a 'articular'oint in ti-e

Measurin# e'osure

Measurin# a ran#e o ariableson an indiidualbasis

e(#( include dietar inta@e

At the sa-e ti-e -easurin# outco-eo interest e( #( obesit

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$ross5sectional "esi#n

Measure-ent o e'osure o interest and

outco-e o interest is carried out at thesa-e ti-e e(#( Bbesit and %or@'eror-ance, Bbesit and %or@ stressC

There is no in5built directionalitas bothe'osure and outco-e are 'resent in thestud sub7ect or ?uite so-e ti-e reerse causation

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*R"51D

Which camefrst?

?? Causality

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$ross5sectional "esi#n

Most ?uantitatie social researche-'los a cross5sectional desi#n(

.nternal alidit %ea@

+ternal alidit

stron# i rando-sa-'les are ta@en, i non rando-sa-'les are ta@en then it beco-es %ea@(

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$ross5sectional studies 5

Stren#ths

seul baseline assess-ent =enerali>able results i 'o'ulation based

sa-'le Stud -ulti'le outco-es and e'osures .--ediate outco-e assess-ent and no loss

to ollo%5u', thereore aster, chea'er, easier H'othesis #eneratin# or causal lin@s Serial sures e#, $ensus +cono-ical H'othesis #eneratin# stud +'osure and outco-e are -easured at the

sa-e ti-e ESna'shot studF(

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$ross5sectional "esi#n 6ea@nesses

Te-'oralit is the -a7or issue

Reerse causation is another one

*rone to bias selection,-easure-entC

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Gias in cross5sectionalstudies

Selection Gias.s stud 'o'ulation re'resentatie o tar#et

'o'ulation8

Measure-ent Gias

Butco-e Misclassi9ed -isdia#nosedC Len#th5biased sa-'lin#

$ases oerre'resented i illness has lon# durationand are underre'resented i short duration(

+'osure Recall bias

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Bdds Ratio BRC

A ratio that -easures the odds o e'osureor cases co-'ared to controls

Bdds o e'osure nu-ber e'osed Inu-ber une'osed

BR u-erator) Bdds o e'osure or cases BR "eno-inator) Bdds o e'osure or

controls

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$alculatin# the Bdds Ratio

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.nter'retation

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.nter'retin# the Bdds Ratio

The odds o exposure or casesare 1!" times the odds oexposure or controls

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.nter'retin# the Bdds Ratio

Those %ith $H" are 1!" times as li@elto be s-o@ers than those %ithout $H"

BR

Those %ith $H" are !"# more li$ely tobe s-o@ers than those %ithout $H"(

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Lon#itudinal "esi#n

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Lon#itudinal "esi#n

Ti-e and cost is inoled

ot used re?uentl

Ti-e is thereso allo% causal inerences to be-ade(

T%o t'es *anel

$ohort

$ase control

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*anel stud

*anel )

A sa-'le is collected at t%o occasions at leastro- sa-e 'eo'le(

$an be collected ro- 'eo'le, household, schooletc

+a-'le

HA+S Gritish household 'anel sure GH*S

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$ohort Stud

$ohort studies are)

*ros'ectie

$o-'are eects o dierent e'osures

Most useul to learn about etiolo#causalrelationshi' o outco-e

Also called ollo%5u' studies, incidencestudies, 'anel studies, lon#itudinal studies,or 'ros'ectie studies

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Reie% o the Adanta#es o a$ohort "esi#n

Te-'oralse?uence bet%een e'osurestatus and outco-e is @no%n -a@in# or

stron#er causal inerences

$an assess -ulti'le outco-es in a de9ned'o'ulation desi#nC

=ood desi#n or co--on outco-es

=ood desi#n or unco--on e'osures

Reie% o the "isadanta#es o

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Reie% o the "isadanta#es oa

$ohort "esi#n

+'ensie

/ualit and etent o inor-ation obtainedis dierent or e'osed than or non5e'osed( This is also @no%n asmisclassifcation a orm o inormationbias.

Reie% o the "isadanta#es o

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Reie% o the "isadanta#es oa

$ohort "esi#n Gias. the sub7ect and the interie%er are a%are othe h'otheses, then the 7ud#-ent is biased btheir @no%led#e addressed b -as@in#

Analtic Gias i analst or statistician haestron# 'reconce'tions

Loss to ollo%5u' es'eciall i -ore sub7ectsare lost ro- one #rou' than another a type oselection bias and/or possible source oconounding

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$ohort "esi#n

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+a-'le) $alculatin# theRelatie Ris@

RRAAG

$$"

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+a-'le) .nter'retin# theRelatie Ris@

Relative Ris$ % 1&'

The ris@ o deelo'in# $H" or a s-o@er is1&' times that or a nons-o@er

BR

The ris@ o deelo'in# $H" is &'# hi(heror a s-o@er than or a nons-o@er(

i h l i

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.nter'retin# the RelatieRis@