# Eleisha's Segment 33: Contingency Tables Protocols and Exact Fisher Test

**To Calculate **

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

There are mxn cells within the table. You are choosing from N events to distribute between the distinct cells. Therefore there are **Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle {m\times n \choose N } }**
distinct tables.

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?

** Back To: ** Eleisha Jackson