chapter 25: paired samples and blocks
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Chapter 25: Paired Samples and Blocks. AP Statistics. Paired/Matched Samples. This situation arises when your groups are NOT independent. What are common situations where this occurs Compare subjects with themselves before and after treatment - PowerPoint PPT PresentationTRANSCRIPT
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Chapter 25: Paired Samples and Blocks
AP Statistics
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Paired/Matched Samples
• This situation arises when your groups are NOT independent.
• What are common situations where this occursCompare subjects with themselves before and
after treatmentCompare subjects with themselves on different
variables• NEED TO THINK!!!!!!!!!!
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Logic
• If the groups are not Independent, you CANNOT use a 2-Sample Test for Means (2-Sample t-Test)
• If the groups are Paired/Matched, you are looking at the differences in the variables and that mean difference
• Since you are now only looking at one variable (difference in variables), you will perform a one-sample t-test.
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Intervals and Tests
• When you groups are paired/matched, the intervals you create and the tests you perform are IDENTICAL (mostly) to the intervals you create and the tests you perform for ONE-SAMPLE T-INTERVAL and ONE-SAMPLE T-TEST
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Assumptions/Conditions
Independence Assumption:Randomization Condition10% Condition
Normal Population Assumption:Need to check each group for normality. SHOW GRAPH.
Nearly Normal Condition
Paired Data Assumption Check reasonableness of this claim. BE CAREFUL
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Things to remember• It is about the differences in the variables• The null hypothesis is typically written as:
• Once you start the “mechanics” of the problem, you will be looking at things like
• You are still dealing with a t-model• Don’t use a two-sample t-test for paired data.• Don’t use a paired –t method when the data are not
paired
0:0 H
dSEd ,
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Calculator HelpFor a paired t test, use the same application as for
a one-sample t-test or one-sample t-interval.
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