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![Page 1: Math Lab PP - editTeacheditteach.org/downloads?download_id=221&filename=Math Lab.pdf · Title: Math Lab PP.ppt Author: Deborah Gump Created Date: 8/16/2009 10:47:28 PM](https://reader033.vdocuments.us/reader033/viewer/2022051913/6004c08dc325ff7dd60858ce/html5/thumbnails/1.jpg)
Usingmathinjournalism Proportion–Explainissuesrelativetothesizeormagnitudeasawhole:
$250,000increaseinBrooklinetaxescomparedto$250,000Pittsburghincrease(residentialnumbersbelowareanillustration,notaccurate)
Percapita–Helpsexplainanissuerelativeto“perindividual”affected
$250,000increaseforcityof3,000is$83.33percapita–establishesarate
$250,000increaseforcityof2millionis12.5centspercapita–establishesarate
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Usingmathinjournalism Percentages–changedividedbytheoriginal,andthenmovedecimalpointtwoplaces
16‐hourdelaysvs.46‐hourdelays 30(increase/change)dividedby16(thebaseline/theoriginalnumber)=
1.875–movedecimaltwo:187.5%increase Percentageisoneofthemostcommonmethodsusedtohelpcommunicatechange
Negativepercentagesarealsopossible‐‐ifthechangeisadecrease
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Usingmathinjournalism Average–Addnumbersanddividebythenumberofelementsinvolved–sameasthemean
Median–Themiddlenumberinanyseries–itisNOTtheaverage
Mediandrawsattentiontothemidpointofnumbers Exampletoillustratethedifferences:Certainemployees’salarieswiththeaverageskewed
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Salariesofthe7employees: $19,000 $20,000 $22,000 $23,000 $24,000 $25,000 $230,000
Median$23,000vs.averageof$51,857
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Consideringmedianvalue Sevenemployees,salaryaverage:$51,857. Thatsoundsattractiveonaverage Considerthemedianofthe7:$23,000 Whythediscrepancy? Whatdoesitreveal? WhydoesajournalistattimeshavetoreportBOTHnumbers?
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Whatismorefairnow? Thismakesthecompany’saveragemuchlargerwhenboss’(consideredanemployee!)salaryincluded
Unfairtoaudiencetosuggestthe$51,000averagesalaryifnootheremployeemakesmorethan$25,000
Audiencecanunderstandmediantohelpmorefullyexplainaninflatedaverage
Thecompanyisnotlyingbysuggestingtheaveragesalaryisalmost$52,000,butyouasthejournalistwouldlooklikeafooltoreportthatnumberwithouttheother
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Majorityvs.plurality Majority–atleast50%+1ofvote Nomajorityifnooneexceeds50% Plurality–differencebetweentopvote‐getterandthesecond‐placefinisher
Donotrefertoapluralityforthedifferencebetweensecondandthird,orthirdandfourth,etc.
DoestheU.S.presidentialelectionrequireamajorityorpluralitytodeterminethewinner?
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Majorityvs.plurality ThreestudentsrunforUSGpresident Resultsof6,959studentsvoting:
Smithwith2,987‐43% Joneswith2,087–30% Dunbarwith1,885–27%(allpercentagesarerounded)
So,whowon?
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Majorityvs.plurality Thiselectionrequiresamajority
So,dowehaveawinner? No–butoneloserandnowarunoff
Smith‐2,987–900‐voteplurality Jones‐2,087–202‐voteedgeoverDunbar Dunbar‐1,885–Nolongerinrace
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Usinginforma?onfromapoll Identifysponsor Exactwordingofquestions Definitionofthepopulationsampled Samplesizeand,ifneeded,responserate Allowanceforsamplingerror Marginoferror
Someinformationgoesintomainstory;othergetsteasedtoyourWebsite
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Usinginforma?onfromapoll Whentheinfowascollected
Whenapollwasconductedcantellyoualotabouttheresultsitfound
Howinfowascollected Phone(mostcommon) Inhomes Inperson Bymail Onthestreet
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Poten?alproblemswithpolls Peopleinterviewedmusttrulybeselectedinrandomfashionifyouwanttogeneralize
Closertheresults,thehardertosayanythingdefinitive Pollsthatclaimtomeasureopiniononsensitive,complicatedissues
Pollsnever,ever,everpredictanoutcome!