quant methods

7/26/2019 Quant Methods

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QUANTITATIVERESEARCH METHODS

Irina Shklovski



Quantitative Research

Methods Include a ide variet! o" la#orator! andnon$la#orator! %rocedures

Involve &easure&ent'




Methods Measure&ent (o%ulations and Sa&%lin)

Rando& Assi)n&ent

*enerali+a#ilit!




Methods Measure&ent (o%ulations and Sa&%lin)

Rando& Assi)n&ent

*enerali+a#ilit! Ti&e

Cross$sectional studies , sin)le e-%eri&ents

.on)itudinal studies , re%eated &easures




Methods Method E-%eri&ents , Quasi$e-%eri&ents

/ehavioral Measures

Questionnaires , Surve!s Social Netork Anal!sis

Archival and Meta$Anal!sis



0hat e ill talk a#out

toda! Measure&ent (o%ulation , Sa&%lin)

Rando& Assi)n&ent

*enerali+a#ilit!

Method

E-%eri&ents , Quasi$e-%eri&ents Questionnaires , Surve!s



Measure&ent 1 Sa&%lin)

S%eci"! !our %o%ulation o" concern

Sa&%lin)

Selectin) res%ondents "ro& %o%ulation o"concern

Rando& sa&%lin)

S!ste&atic selection

Strati2ed sa&%lin)

Convenience sa&%lin)

Sno#all sa&%lin)



Sa&%lin) /iases

Non$res%onse #ias /e %ersistent

O3er incentives and reards

Make it look i&%ortant

Volunteer #ias

So&e %eo%le volunteer relia#l! &ore thanothers "ora variet! o" tasks



Rando& assi)n&ent

Di3erent "ro& rando& sa&%lin)

Mostl! used "or e-%eri&ents or 4ua+i$e-%eri&ents

(rotects a)ainst unsus%ected sources o" #ias

Does NOT )uarantee to #alance out thedi3erences #eteen %artici%ants

Chance is .UM(5



*enerali+a#ilit!

Ho do !ou kno that hat !ou "ound in!our research stud! is6 in "act6 a )eneraltrend7

Does A reall!6 ala!s cause /7

I" A ha%%ens6 is / reall! as likel! toha%%en as !ou clai&7 Ala!s7 Under

certain conditions7



Association vs8 Causalit!

Thanks to

Sara 9iesler"or these)ra%hs:



E-%eri&ents , Quasi$e-%eri&ents

e-;%er;i;&ent (ronunciation< =ik$>s%er$?$&?nt also $>s%ir$= @unction< noun Et!&olo)!< Middle En)lish6 "ro& An)lo$@rench

es%eri&ent6 "ro& .atin e-%eri&entu&6 "ro& e-%eriri Date< Bth centur!

An o%eration or %rocedure carried out undercontrolled conditions to discover an unknone3ect or la6 to test or esta#lish a h!%othesis6or to illustrate a knon la



E-%eri&ents , Quasi$e-%eri&ents 9e! "eature co&&on to all e-%eri&ents<

To deli#eratel! var! so&ethin) in order todiscover hat ha%%ens to so&ethin) else

later To seek the e3ects o" %resu&ed causes



An E-%eri&ent is

A controlled e&%irical test o" a h!%othesis8

H!%otheses include<

A causes / A is #i))er6 "aster6 #etter than / A chan)es &ore than / hen e do

To re4uire&ents< Inde%endent varia#le that can #e &ani%ulated De%endent varia#le that can #e &easured



E-%eri&ents in Research

Co&%arin) one desi)n or %rocess toanother

Decidin) on the i&%ortance o" a

%articular "eature in a user inter"ace Evaluatin) a technolo)! or a social

intervention in a controlled environ&ent

@indin) out hat reall! causes an e3ect @indin) out i" an e3ect reall! e-ists



Re&e&#er

E-%eri&ents e-%lore the e3ects o" thin)sthat can #e MANIPULATED

#ut there is a caveat



T!%es o" E-%eri&ents

Randomized 1 unitsF%artici%antsassi)ned to receive treat&ent oralternative condition rando&l!

Quazi 1 no rando& assi)n&ent Natural – contrastin) a naturall!

occurrin) event i8e8 disaster ith a

co&%arison condition



I" !our stud! involvese-%eri&ents E-%eri&ental desi)n<

Shadish 08R86 Cook T8D8 , Ca&%#ell (8T8 GGExperimental and Quasi-Experimental Design forGeneralized Causal Inference8 /oston6 Mass<Hou)hton Miin

E-%eri&ental data anal!sis<

/runin)6 J8 .8 , 9int+6 /8 .8 KKL8 Computationalhandboo of statistics !"th ed#$8 Ne 5ork<.on)&an#



Questionnaires , Surve!s

Sel"$re%ort &easures Questionnaires , surve!s

Intervies

Diaries T!%es

Structured

O%en$ended



Questionnaires , Surve!s

Advanta)es Sa&%le lar)e %o%ulations chea% on

&aterials , e3ort

Ecientl! ask a lot o" 4uestions Disadvanta)es

Sel"$re%ort is "alli#le

Res%onse #iases are unavoida#le



Res%onse #iases

Rel!in) on %eo%les &e&or! o" events ,#ehaviors E&otional states can %ri&eP &e&or!

Recenc! e3ects Routines are deceivin)

Social desira#ilit! Solution< none that are si&%le

5ea$sa!in) Solution< var! the direction o" res%onse

alternatives



*eneral Surve! /iases

%ampling 1 are res%ondents re%resentativeo" %o%ulation o" interest7 Ho ere the!selected7

Co&erage 1 do all %ersons in the %o%ulationhave an e4ual chan)e o" )ettin) selected7

'easurement – 4uestion ordin) ,orderin) can o#struct inter%retation

Non-response 1 %eo%le ho res%ond di3er"ro& those that do not



Desi)n is 9E5

(ormat 1 #ooklet6 %rinted vertical6 one$sided

Question ordering 1 earlier 4uestions can

%ri&e ansers to later 4uestions )age la*out 1 )rou% si&ilar ite&s , use

consistent "onts and res%onse cate)ories

)re-testing 1 conduct think$alouds ithvolunteers de&o)ra%hicall! si&ilar toe-%ected %artici%ants



Co&&on (ro#le&s

Avoid co&%licated , dou#le$#arrel4uestions Co&%le-it! increases errors , non$res%onse

Navi)ation is %ara&ount 1 &ake sure thesurve! is EAS5 to "ollo

O%en$ended 4uestions The si+e o" the 2eld allotted ill deter&ine the

nu&#er o" ords Incentive is ke!

/UT a&ount di3erences have little i&%act



I" !our stud! involvessurve!s Desi)nin) surve!s<

Dill&an6 D8 A86 S&!th6 J8 D86 , Christian6 .8 M8 GK8Internet+ mail+ and mixed-mode sur&e*s , the tailoreddesign method !rd ed#$# Ho#oken6 N8J8< 0ile! , Sons#

@oler6 @8 J8 KK8 Impro&ing sur&e* .uestions ,design and e&aluation# Thousand Oaks< Sa)e(u#lications#

Anal!+in) data<

Cohen6 J86 Cohen6 (86 0est6 S86 , Aiken6 .8 G8 /pplied multiple regression0correlation anal*sis forthe beha&ioral sciences !rd ed#$8 Mahah6 NJ<.arence Erl#au& Associates8



So' hat7

Di3erence #eteen 4uantitative &ethodsis in the 4uestions the! can anser

There are a .OT o" &ethods and even&ore statistical techni4ues

Re)ardless o" the &ethod6 i" its not ane-%eri&ent6 !ou CAN NOT %rove causation



Thin)s e did NOT talka#out Relia#ilit! assess&ents

Validit! assess&ents

Statistical anal!sis o" data

Inter%retation o" results

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