handout 5 reliability & validity

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1、阳光家教网www.ygjj.com英语学习资料Lecture5ReliabilityandValidity信度和效度5.1Reliability5.1.1WhatIsReliabilitySeliger&Shohamy(p.185):Reliabilityofameasurementrefersto“whetherthedatacollectionprocedureisconsistentandaccurate.”Trochim(2005):Reliabilityofameasurementreferstotheconsistency,stabilityorrepeatab

2、ilityofthemeasurementofsomephenomena.信度是指采用一种方法对一组对象进行测量时，其结果的一致性和稳定性。lTwokeywordsindefiningreliability:FConsistencyFRepeatability(stability)lSignificanceofReliabilityinResearchIfthedataweuseareunreliable,theconclusionwehavemadeonthedataisofnosignificanceatall.5.1.2ReliabilityinQNDatalSamp

3、lingerrorinaQNresearch凡测量必有误差，误差由机率因素支配，在抽样中有抽样误差SamplingError。抽样误差不可避免，但可以控制在一定范围内。lThereisanotherkindoferrorincollectingandmeasuringdata.Itincludes：-randomerror随机误差-systematicerror系统误差Trochim(2005:61):“Randomerroriscausedbyanyfactorsthatrandomlyaffectmeasurementofthevariableacrossthesamp

4、le.”Randomerrordoesnothaveanyconsistenteffectsacrosstheentiresample.Trochim(2005:61):“Systematicerroriscausedbyanyfactorsthatsystematicallyaffectmeasurementofthevariableacrossthesample.”Systematicerroraffectsthecentraltendencyoraverageofadistribution.5.1.3StatisticalTheorybehindReliability

5、inaQNStudy信度的统计学原理l测量值＝实测值＋误差：X=T+el其理论基础：TheTrueScoreTheory真值理论:X:我们观察或测量后得到的值T:真实值（即我们想测量的理想值）e:随机误差randomerror5.1.4TechniquesinTestingReliabilityl信度指标多以相关系数correlationcoefficient表示（0-1之间）。l信度系数的含义：越接近1，其信度系数越高，也就越接近真值。7第7页共7页阳光家教网www.ygjj.com英语学习资料ForExample,areliabilityof0.5meansthatab

6、outhalfofthevarianceoftheobservedscoresislikelytobethetruevalue(T)andhalfislikelytobetheerror(e).Areliabilityof0.8meansthevariability差异性isabout80%trueabilityand20%error,andsoon.l4methodsareoftenusedtotestreliability：(1)Test-retest再测法F用同一个测量工具，对同一组受试者，前后测试2次，然后计算两次结果的相关系数（又称稳定系数）（跨时间的一致性），F

7、Usedtoassesstheconsistencyofameasurefromonetimetoanother.(2)Parallel-Forms(EquivalentForm)(Alternativemethod)复本（平行）法F同一组受试接受2次不同的测试（测试工具同类不同题），然后计算两者的相关系数。FUsedtoassesstheconsistencyoftheresultsoftwotestsconstructedinthesamewayfromthesamecontentdomain.(3)Inter