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Lecture 13

PSYC1010 Lecture 13: Chapter 5: Lecture Notes


Department
Psychology
Course Code
PSYC 1010
Professor
Harvey Marmurek
Lecture
13

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Chapter5StatisticalPredictionandRegression Jan.
26th/28th
Regression
● Regressioncanbemoreaccuratethanthemeanwhenmakingaprediction.
● analysescreateamathematicalmodelformakingpredictionsaboutthescoreona
dependentvariable
● bivariateregressionreferstothecasewherethereisonedependentvariableandone
predictorvariable
○ bivariatemeanstherearetwovariables:xandy
● multipleregressioninvolvesmorethanonepredictorvariableandwillnotbecovered
inthiscourse
● ifapredictorvariableandadependentvariablearecorrelated,theregressionmodel
willleadto“better”predictionsthanpredictingthateveryscorewillequalthemean
StandardizedRegression
● standardreferringtostandarddeviation
● predictsthezscoreofthedependentvariablefromthezscoresofthepredictor
variable.
predictedZy=(B)(Zx)there’sahatontopoftheZy,butitmeans“predicted”,Bis
beta
○ thepredictedZy=beta*Zx
○ inbivariateregression:B=r
xy
○ predictedZy=r(thecorrelation)multipliedbytheknownZxscore
● Regressiontothemean:
○ predictedZyiscloserto0thanisZx
○ “sophomorejinx”(sports)doingworsethesecondyearthanyoudidinthefirst,
peoplesayyoudidsowellyouhadfirstyouhadnowheretogobuttowards
themean
○ anotherexample:ifyouhavereallytallparents,you’llbetallerthanaveragebut
regresstothemeanandbeshorterthanyourparents.Sameforshort:really
shortparents,kidwillbeshorterthanaveragebutregresstowardsthemean
andbetallerthantheparents
○ theweakerthecorrelation,thegreaterisregressiontothemean
○ importantinpsychbecauseregressiontothemeanmeansthatregardlessof
whatyoudoextremegroupswillimprove/digressregardlessofyour
interventionbecausetheyregresstothemean.Youshoulduseacontrolthat
doesn’treceiveinterventiontokeepaneyeonregressiontothemean.
Example:
A.Youknowthattheaveragerequiredamountoftimetofinishthetaskis8.24minutes.With
noadditionalinformation,whatisyourbestguessastotheamountoftimeitwilltakeyouto
finishthetask?
8.24minutes,becauseitisthemeanandyouhavenoadditionalinfo
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