Stats 309 13-1

Stats 309 13-1 - 13.1 Inference about the difference...

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13.1 Inference about the difference between 2 means – Independent samples What if we want to compare 2 different populations? We may be interested in comparing two population means. For example, we may want to compare the mean GPA of men versus women. One way is to draw two independent samples . For example, we could be interested in seeing how a speed reading course affects GPA. We could get a sample of people who took the course and get a separate sample of people who didn’t take the course and then compare the GPA’s. Or, we could do a matched pairs sample . This is where there is some relationship between a sample point in one sample and a sample point in another sample. For example, ‘before and after’ experiments are matched pairs. With the speed reading course example, we could get a sample of people who haven’t had the course, record their GPA. Then have them take the speed reading course, then record their GPA again. This would be a matched pair and the relationship between the two groups is that they are the same people, just with a before and after reading.
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You can also have a matched pair experiment if you use a pair of twins, siblings, or spouses. Or, as long as you take the time to find two experimental units that are similar to begin with, then put one in
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Stats 309 13-1 - 13.1 Inference about the difference...

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