PSY202H5 Lecture 4: Lecture 4
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Lecture 4: Testing hypotheses concerning variances 2
• What kind of experimental design is this?
• Two independent group design, one measure per subject
• What kind of data are being collected?
• Continuous
• Do we know the population variances for the two groups?
• No.
• What do we know about the distribution of scores in each group.
• The frequency histograms indicate the sample scores are unimodal and mound shape.
Hence it is reasonable to assume that the two population have normal distributions.
However, we do not know the mean and standard deviation of each population.
• What kind of test of the difference in means should we consider..
• A t-test of the difference between the two population means is 0.
• What are the requirements for such a test.
• Normal distributions of the sample means, and equal variances in the two groups.
• How to test for equal variance in a two-group independent random sampling (between
subject) design.
Testing whether two variances are equal
• If the variance of the experimental group equals that of the control group then
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