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Lecture7-Jan+28th-reliability-validity2

Lecture7-Jan+28th-reliability-validity2 - Quiz5dueNOW...

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Quiz 5 due NOW Quiz 6 due will be available after class. Due date is nextTHURSDAY, before class Exam’s scores will be available by end of week We’ll discuss results next tuesday
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The problem of artifacts Reliability Validity
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The problem of artifacts Uncontrolled human aspects of the research situation that CONFOUND researcher’s conclusions
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Participants related artifacts (aka Demand Characteristics) Cooperative Tries to give the ‘best performance’ that matches the presumed hypothesis Non‐Cooperative Doesn’t care about study or tries to sabotage results Defensive Wants to be portrayed in good light
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Researchers related artifacts Observer bias Over‐ or under‐estimation of what was observed Expectancy bias ‘Self‐fulfilling prophecy’
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Blind experiments Deception ‘Double blind’ Automation (Standardization) Computers Recording instructions Question participants
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The problem of artifacts Reliability Are our measurements precise? Validity Are we really measuring what we think we are measuring?
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Extent to which measurements are free of random errors Random error : nonsystematic mistakes in measurement misreading a questionnaire item observer looks away when coding behavior nonsystematic misinterpretations of a behavior
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What are the implications of random measurement errors for the quality of our measurements?
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O =T + E + S O = a measured score (e.g., performance on an exam) T = true score (e.g., the value we want) E = random error S = systematic error O =T + E (we’ll ignore S for now, but we’ll return to it later)
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O =T + E The error becomes a part of what we’re measuring!
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