Psyc_315_-_Winter_2010_-_Class_21

# Psyc_315_Winter_20 - Dependent Samples t-Test Practice Problems Recap of Last Class A research design that involves dependent samples is one where

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Dependent Samples t-Test Practice Problems 2 Recap of Last Class • A research design that involves dependent samples is one where the observations from one sample are related in some way to those from the other. • Before vs after (repeated measures) • Or two matched samples. • Essentially the same as the single-sample t-test. One major distinction is that it is based on difference scores (D) rather than raw scores (X scores). • The sign of each D score tells you the direction of the change. The sample of difference scores will serve as the sample data for the hypothesis test. 3 Recap of Last Class • Interested in knowing what would happen if every individual in the population were measured in two treatment conditions (X 1 and X 2 ) and a difference score were computed for every one. • The null hypothesis states that there is no effect, no change or no difference. • Specifically interested in the mean of the population of difference scores (M D ). Some will show positive difference scores and some will show negative scores, but the differences will balance out to 0.

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4 Recap of Last Class • The variance and standard deviation of the population of difference scores are estimated from the sample difference scores. • The distribution of means of difference scores has a mean of 0, the same as the mean of the population of difference scores. • The standard deviation of the distributions of means of difference scores (i.e., estimated standard error) is the estimated population standard deviation of difference scores divided by the square root of the sample size. 5 Steps of 2-sample Dependent Means • Step 1: Formulate Hypotheses • Step 2: Sample distribution • Step 3: Calculate appropriate statistics • Step 4: Determine critical cut-off - Need alpha - 1 or 2 tailed depending on question
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## This note was uploaded on 04/29/2010 for the course PSYCH 315 taught by Professor Afroditipanagopoulos during the Winter '10 term at Concordia Canada.

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Psyc_315_Winter_20 - Dependent Samples t-Test Practice Problems Recap of Last Class A research design that involves dependent samples is one where

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