11_Lecture11_tTest_2DependentSamples_0328_Spring11

11_Lecture11_tTest_2DependentSamples_0328_Spring11 - XI t...

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1 PSY207 B Spring 2011 Psychological Statistics XI. t Test for Two Dependent Samples Learning Objectives t Test for Two Dependent Samples • Dependent samples • Difference scores • Null and alternative hypothesis • Mean • Standard Error • Effects of dependent samples on SE t Test for Two Dependent Samples • t ratio • Repeated measures and counter-balancing • Assumptions XI. t Test for Two Dependent Samples 11.1 Overview So far, we’ve discussed . . . • t test for one sample • t test for two independent samples • Now we turn to . . . • t test for two dependent samples
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2 Two Dependent Samples • Each observation in one sample is paired with another single observation in the other sample • Generally known as • Dependent, related, or correlated samples • Special cases • Within subjects • Repeated measures • Matched subjects • What are the effects of caffeine on memory? Example Caffeine Placebo Measure Memory Measure Memory Group A Group B Dependent Samples • We want to make certain that groups A and B are matched on cognitive factors, such as memory span • E.g., We want to match on basic memory capacity before administering caffeine and placebo • How could we match the participants in the two groups? • We might test twins • Matched subjects design Dependent Samples • Because we're testing twins, the two groups (A and B) should differ little on cognitive factors • We have controlled for possible cognitive differences between A and B Example: Scores on Memory Test after Caffeine (A) or Placebo (B) Caffeine Measure Memory Group A Placebo
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This note was uploaded on 04/20/2011 for the course PSY 207 taught by Professor Pfordesher during the Spring '07 term at SUNY Buffalo.

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11_Lecture11_tTest_2DependentSamples_0328_Spring11 - XI t...

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