10_Lecture10_tTest_2IndependentSamples_0323_Spring11-1

10_Lecture10_tTest_2IndependentSamples_0323_Spring11-1 - X....

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1 PSY207 B Spring 2011 Psychological Statistics X. t Test for Two Independent Samples Learning Objectives t Test for Two Independent Samples • Null and Alternative Hypotheses • t ratio • Pooled variance • Standard error • Degrees of freedom • Cohen’s d • Proportion of Variance Accounted for X. t Test for Two Independent Samples 10.1 Overview Overview • Previous t test for one sample compared a single sample mean to a hypothesized population mean • What if we want to compare two samples means to determine if they are significantly different? • Independent samples • Samples in which the behavior of the members of one sample is not related to the behavior of the members of the other sample Example • When a car fails to go on a green light, are the people behind the car more likely to honk if the car is "low status" than if the car is "high status"? • Two independent samples • 1. People stuck behind a low status car • 2. People stuck behind a high status car • Question • Who will honk the fastest?
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2 X. t Test for Two Independent Samples 10.1 Overview 10.2 Obtaining the t Statistic Two Independent Samples • Measure the time in seconds from the turn of the light to the honk • We are interested in the difference between the two sample means: M 1 -M 2 • There are three possible outcomes Possible Outcome #1 • There is no difference between the sample means M 1 2 = 0 Possible Outcome #2 • Sample mean 1 is larger than sample mean 2: M 1 2 > 0 Possible Outcome #3
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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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10_Lecture10_tTest_2IndependentSamples_0323_Spring11-1 - X....

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