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METHODS OF DATA COLLECTION

AppliedSta+s+csandCompu+ngLab

IndianSchoolofBusiness

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Learninggoals

Importanceofdata Howdoweobtaindata? Randomiza=on Sampling

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Data

Recorded,relevantinforma=on Notnecessarilyjustnumbers Anyrelevantfacts,figures,observa=onsordescrip=onsofthings

Butwhydoweneedit?

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Whydata?

Bases/Rawmaterialforanalysis Helpprovideanswerstoques=onswecannotanswerright

away

Empiricalsupportto(against)theories Howdoweanswerthisques=on:

Doindividualswithlargerwaistcircumferenceshavelargerintra-abdominaladipose=ssue(AT)area?

Goodideatogatherrelevantinforma=on Studyafewindividuals,notpossibletostudyallindividuals Data:

Age Waistcircumference ATarea

Trytofindamodeltorelatethese

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Sources:Primary

Originalsourcesfromwhichresearchersdirectlycollect

Firsthandinforma=on Collectedthrough:

Observa=on(AT-WC) Interviewing(Stores-Customers)

Classifiedas: Completeenumera=on Sampling Designedexperiment

Researchercancollectaccuratelyandaccordingtoresearchneeds

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Sources:PrimaryCompleteenumera=on

Onewaytogatherusefulinforma=on Collectdatafromeachandeveryunitinthepopula=on Appliedwhereinforma=ononallunitsunderstudyis

needed:

Popula=onCensus(popula=on:allindividualsinthecountry) Prepara=onofvoterslist(popula=on:allindividualswithvoter

Ids)

Selec=onfrommanyapplicantsforajobetc

Socialnetworkingsitestraceallyourac=vi=es,onlineshoppingetc

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IsCompleteenumera=onthebest

method?

Timeandmoneyexpenses Neednotnecessarilyprovideaccurateinforma=on,

notfreeoferrors(non-samplingerrors):

Evenincensusthereisalwaysover/underenumera=oni.e.incompletecoverage

Tabula=on/dataentryerrors Errorsduetodifficultyinorganizingandimplemen=ngout

surveysoflargemagnitudes

Mostimportantly,completeenumera=onmightnotbenecessary

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NeedforSampling

Onlypartofthepopula=onisstudied Certaincircumstancesunderwhichitispreferredovercompleteenumera=on?LimitedresourcesProvisionforapermissibleerrorexistsDestruc=vestudies

Ideaisthatifthesampleconsideredisrepresenta+veofthepopula+onthatitis

takenfrom,theresultsderivedfromitcanbegeneralizedtothepopula+on.

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Sampling:Example

Thecarsdata NotpossibletostudyeveryusedcarinUS Sampleofusedcars Carsofallmakes,models,enginesizesetcincluded

AT-WCexample: Dataonlyonmen Notrepresenta=veifinterestisinmeasuringCVDriskfor

women

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Representa=veSamples

Whichsamplesarerepresenta=ve? Samplesarebiasedifsomecharacteris=csofpopula=onareover/underrepresented

Resultsfromthesesamplescannotbeadjusted Weneedunbiased&representa=vesamples

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Randomiza=on

Toovercomebias Shufflingadeckofcardsbeforedealing s=rringapotofsoupbeforetas=ng

Randomselec=onisfair Randomsamplingmeanssamplingbasedoneach

popula=onunithavingapar=cularchanceofbeingselectedintothesample

Inapopula=onwith60%menand40%womenasampledrawnwithwomenhavingagreaterchanceofselec=on

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Sampling:Advantages

Timeandmoneysaved Moreaccurate/reliableinforma=on Opera=onalflexibility

Notanewidea!Appliedindaytodaylife:

TasteonlyaspoonfulofsoupOnlyahandfullofgrainsareexaminedbefore

buyingtheen=resack

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Sampling:Disadvantages

Samplingerrors: Boundtooccur Duetofactthatonlyapartofpopula=onis

considered Nonsamplingerrorsaswell

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Sampling:Trivia

Morepopularlyusedthancompleteenumera=on

Samplingmethoddependsonques=onathand

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Source:PrimaryExperimentalDesign

Anexperimentisatest Conductedtostudyaprocessorasystem Outcomenotknownwithcertainty Inves=gatorcancontrolformanycondi=ons Dataarisefromsuchexperiments

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Source:PrimaryExperimentalDesign,Example

Toconductanexperimentoneyefocus=me Effectofdistanceofobjectfromeyeonfocus=me

4differentdistancesand5subjects Differencesbetweenindividuals(moreonthisinfuturesessions)

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Source:PrimaryExperimentalDesign,Example

Theresultsoftheexperimentorthedatacollectedwas:

DISTANCE(

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ExperimentalDesignAdvantagesandDisadvantages

Advantages:

AccurateaswecancontrolforerrorRandomobserva=ons(wedonotknowresultsin

advance)Disadvantages:

ExperimenterbiasCannotdesignexperimentsforallstudies(cars

example)

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Source:Secondary

Havealreadybeencollectedandcompiled Readilyavailable E.g.:scoresdata!Theschoolalreadyhasamarksheetforeachstudent!

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Source:Secondarycontd..

PublishedsourcesGovt.publica=ons(RBI,LabourGazee,NSSO

etc)

Interna=onalbodies(WHO,IBRD,IMFetc) Researchscholars OtherSecondarySources

CompustatProwessIndiaStat

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Secondarysources:Advantages

Easilyavailable 1sthandinforma=onmightnotbeeasytocollect

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Secondarysources:Disadvantages

Format Missingdata Outdated:

Wanttostudypovertyratesbutdefini=onofthepovertylinehaschangedovertheyears

Differentsources: Dataavailablefrommanysources Havetobemerged E.g.:wehavepricesfromonesecondarysourceindollarsand

otherdatainrupeesfromanothersource.Mergingthemisnoteasy.

Needtoconsiderexchangeratesatdifferent=mes,Purchasingpowerparitydifferences

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Thankyou