Chapter8part1

# Chapter8part1 - Paired Samples versus Independent Samples...

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Paired Samples versus Independent Samples Paired Design 1 With paired data, we are interested in comparing the responses within each pair. We will analyze the differences of the responses that form each pair. Paired Data: Response = Annual Salary (in \$1000s) 15 45 50 16 56 Wife Response 20 31 50 30 72 Husband Response -5 14 0 -14 -16 Difference = Wife - Husband Mean Difference = -4.2 15 - 20 = 56 - 72 = 16 - 30 = 50 - 50 = 45 - 31 = Paired Design 2 DEFINITION: We have paired or matched samples when we know, in advance, that an observation in one data set is directly related to a specific observation in the other data set. It may be that the related sets of units are each measured once (Paired Design 1), or that the same unit is measured twice (Paired Design 2). In a paired design, the two sets of data must have the same number of observations.
Independent Samples Design Independent Samples Data: Response = Annual Salary (in \$1000s) 15 45 50 16 56 Women Response 20 31 50 30 72 Men Response Mean for Women = 36.4 Mean for Men = 40.6 Difference in the means = 36.4 - 40.6 = -4.2 In the two independent samples scenario, we will compare the responses of one treatment group as a whole to the responses of the other treatment group as a whole. We will calculate summary measures for the observations from one treatment group and compare them to similar summary measures calculated from the observations from the other treatment group. DEFINITION: We have two independent samples when two unrelated sets of units are measured, one sample from each population, as in Independent Samples Design 11.3. In a design with two independent samples, although the same sample size is often preferable, the sample sizes might be different.

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Let’s Do It! Paired Samples versus Independent Samples (a) Three hundred registered voters were selected at random, 30 from each of 10 midwestern counties, to participate in a study on attitudes about how well the president is performing his job. They were each asked to answer a short multiple-choice questionnaire and then they watched a 20-minute video that presented information about the job description of the president. After watching the video, the same 300 selected voters were asked to answer a follow- up multiple-choice questionnaire. The investigator of this study will have two sets of data: the initial questionnaire scores and the follow-up questionnaire scores. Is this a paired or independent samples design? Circle one:
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Chapter8part1 - Paired Samples versus Independent Samples...

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