PSYC 331 Lecture 17 -- 2 independent t-test_1

PSYC 331 Lecture 17 -- 2 independent t-test_1 - PSYC 331...

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1 PSYC 331 Lecture 17 The t-statistic for Two Independent Samples
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2 Overview In this lecture, we will… Review the t statistic Learn about independent measures Discuss pooled variance Perform hypothesis tests with independent measures t statistic Measure effect size for the independent measures t statistic Discuss what influences effect size Discuss assumptions of the independent measures t statistic
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3 Single Sample t Statistic Review Single sample t test: Uses data from a single sample Test hypothesis about the population mean Population standard deviation ( σ ) is un known Uses the formula: t = where s M = Effect size is measured to determine actual magnitude of the effect Cohen’s d r 2 – measures percentage of variability accounted for by treatment effect M- μ s M s n
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4 What is an “independent sample”? “A research design that uses a separate sample for each treatment condition (or for each population) is called an independent-measures research design or a between- subjects design.” (G&W, pg. 310) Later on, we will discuss repeated- measures (a.k.a within-subjects design)
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5 Independent t statistic Uses data from 2 separate samples to make inferences about the mean difference between 2 populations (or between 2 treatments)
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PSYC 331 Lecture 17 -- 2 independent t-test_1 - PSYC 331...

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