Usingmathinjournalism Proportion–Explainissuesrelativetothesizeormagnitudeasawhole:

 $250,000increaseinBrooklinetaxescomparedto$250,000Pittsburghincrease(residentialnumbersbelowareanillustration,notaccurate)

 Percapita–Helpsexplainanissuerelativeto“perindividual”affected

 $250,000increaseforcityof3,000is$83.33percapita–establishesarate

 $250,000increaseforcityof2millionis12.5centspercapita–establishesarate

Usingmathinjournalism Percentages–changedividedbytheoriginal,andthenmovedecimalpointtwoplaces

  16‐hourdelaysvs.46‐hourdelays  30(increase/change)dividedby16(thebaseline/theoriginalnumber)=

  1.875–movedecimaltwo:187.5%increase Percentageisoneofthemostcommonmethodsusedtohelpcommunicatechange

 Negativepercentagesarealsopossible‐‐ifthechangeisadecrease

Usingmathinjournalism Average–Addnumbersanddividebythenumberofelementsinvolved–sameasthemean

 Median–Themiddlenumberinanyseries–itisNOTtheaverage

 Mediandrawsattentiontothemidpointofnumbers  Exampletoillustratethedifferences:Certainemployees’salarieswiththeaverageskewed

Salariesofthe7employees: $19,000 $20,000 $22,000 $23,000  $24,000 $25,000  $230,000

 Median$23,000vs.averageof$51,857

Consideringmedianvalue  Sevenemployees,salaryaverage:$51,857. Thatsoundsattractiveonaverage Considerthemedianofthe7:$23,000 Whythediscrepancy? Whatdoesitreveal? WhydoesajournalistattimeshavetoreportBOTHnumbers?

Whatismorefairnow? Thismakesthecompany’saveragemuchlargerwhenboss’(consideredanemployee!)salaryincluded

 Unfairtoaudiencetosuggestthe$51,000averagesalaryifnootheremployeemakesmorethan$25,000

 Audiencecanunderstandmediantohelpmorefullyexplainaninflatedaverage

 Thecompanyisnotlyingbysuggestingtheaveragesalaryisalmost$52,000,butyouasthejournalistwouldlooklikeafooltoreportthatnumberwithouttheother

Majorityvs.plurality Majority–atleast50%+1ofvote Nomajorityifnooneexceeds50% Plurality–differencebetweentopvote‐getterandthesecond‐placefinisher

 Donotrefertoapluralityforthedifferencebetweensecondandthird,orthirdandfourth,etc.

 DoestheU.S.presidentialelectionrequireamajorityorpluralitytodeterminethewinner?

Majorityvs.plurality ThreestudentsrunforUSGpresident Resultsof6,959studentsvoting:

  Smithwith2,987‐43%  Joneswith2,087–30% Dunbarwith1,885–27%(allpercentagesarerounded)

  So,whowon?

Majorityvs.plurality Thiselectionrequiresamajority

  So,dowehaveawinner? No–butoneloserandnowarunoff

  Smith‐2,987–900‐voteplurality  Jones‐2,087–202‐voteedgeoverDunbar Dunbar‐1,885–Nolongerinrace

Usinginforma?onfromapoll  Identifysponsor Exactwordingofquestions Definitionofthepopulationsampled  Samplesizeand,ifneeded,responserate Allowanceforsamplingerror Marginoferror

  Someinformationgoesintomainstory;othergetsteasedtoyourWebsite

Usinginforma?onfromapoll Whentheinfowascollected

 Whenapollwasconductedcantellyoualotabouttheresultsitfound

 Howinfowascollected  Phone(mostcommon)  Inhomes  Inperson  Bymail Onthestreet

Poten?alproblemswithpolls Peopleinterviewedmusttrulybeselectedinrandomfashionifyouwanttogeneralize

 Closertheresults,thehardertosayanythingdefinitive Pollsthatclaimtomeasureopiniononsensitive,complicatedissues

 Pollsnever,ever,everpredictanoutcome!