statsmodels.stats.contingency_tables.Table2x2.symmetry¶

Table2x2.
symmetry
(method='bowker')¶ Test for symmetry of a joint distribution.
This procedure tests the null hypothesis that the joint distribution is symmetric around the main diagonal, that is
\[\]p_{i, j} = p_{j, i} for all i, j
Returns:  A bunch with attributes
 statistic (float) – chisquare test statistic
 pvalue (float) – pvalue of the test statistic based on chisquare distribution
 df (int) – degrees of freedom of the chisquare distribution
Notes
The implementation is based on the SAS documentation. R includes it in mcnemar.test if the table is not 2 by 2. However a more direct generalization of the McNemar test to larger tables is provided by the homogeneity test (TableSymmetry.homogeneity).
The pvalue is based on the chisquare distribution which requires that the sample size is not very small to be a good approximation of the true distribution. For 2x2 contingency tables the exact distribution can be obtained with mcnemar
See also