Abstract
SEVERAL algebraically equivalent methods are in use for calculating χ2 for a 2 × 2 contingency table; but there is one attractive algorithm that does not seem to have been described. Write the table and its marginal totals in the usual notation: where N = a + b + c + d. Let A be the difference between the two observed ratios when the table is read across, so that . Similarly, let D be the difference when the table is read downwards, so that . Then it can be shown that .
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WOOLF, B. Calculation of χ2 for a 2 × 2 Table. Nature 168, 1087 (1951). https://doi.org/10.1038/1681087a0
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DOI: https://doi.org/10.1038/1681087a0
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