Segment 33. Contingency Table Protocols and Exact Fisher Test

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Watch this segment

(Don't worry, what you see statically below is not the beginning of the segment. Press the play button to start at the beginning.)

The direct YouTube link is http://youtu.be/9Qrkw5UfAmQ

Links to the slides: PDF file or PowerPoint file

Problems

To Calculate

1. How many distinct m by n contingency tables are there that have exactly N total events?

2. For every distinct 2 by 2 contingency table containing exactly 14 elements, compute its chi-square statistic, and also its Wald statistic. Display your results as a scatter plot of one statistic versus the other.

To Think About

1. Suppose you want to find out of living under power lines causes cancer. Describe in detail how you would do this (1) as a case/control study, (2) as a longitudinal study, (3) as a snapshot study. Can you think of a way to do it as a study with all the marginals fixed (protocol 4)?

2. For an m by n contingency table, can you think of a systematic way to code "the loop over all possible contingency tables with the same marginals" in slide 8?

Activity

Chess contingency tables