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, non-parametric tests.ppt

, non-parametric tests.ppt
内容要点:
, non-parametric tests,The?paired?t-test,?non-parametric?tests,?and?ANOVAJuly 13, 2004Review: the Experiment (note: exact numbers have been altered)l Grade?3?at?Oak?School?were?given?an?IQ?test?at?the?beginning?of?the?academic?year?(n=90).l Classroom?teachers?were?given?a?list?of?names?of?students?in?their?classes?who?had?supposedly?scored?in?the?top?20?percent;?these?students?were?identified?as?“academic?bloomers”?(n=18).l BUT: the children on the teachers lists had actually been randomly assigned to the list.l At?the?end?of?the?year,?the?same?I.Q.?test?was?re-administered.The resultsChildren?who?had?been?randomly?assigned?to?the?“top-20?percent”?list?had?mean?I.Q.?increase?of?12.2?points?(sd=2.0)?vs.?children?in?the?control?group?only?had?an?increase?of?8.2?points?(sd=2.5)Confidence interval (more information!!)95%?CI?for?the?difference:?4.0±1.99(.64)?=?(2.7?–?5.3)t-curve?with?88?df’s?has?slightly?wider?cut-off’s?for?95%?area?(t=1.99)?than?a?normal?curve?(Z=1.96)The Paired T-testThe Paired T-testl Paired?data?means?you’ve?measured?the?same?person?at?different?time?points?or?measured?pairs?of?people?who?are?related?(husbands?and?wives,?siblings,?controls?pair-matched?to?cases,?etc.?l For?example,?to?evaluate?whether?an?observed?change?in?mean?(before?vs.?after)?represents?a?true?improvement?(or?decrease):Null?hypothesis:?difference?(after-before)=0The differences are treated like a single random variableXi Yi Xi - YiX1 Y1 D1X2 Y2 D2X3 Y3 D3X4 Y4 D4… … …Xn Yn Dn T=Example Databaseline Test2 improvement10 9 -110 12 +29 13 +48 8 012 11 -11

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