Compute McNemar's test (two two-sided variants) in Python

mcnemar.py

import scipy.stats


def mcnemar_p(n1: int, n2: int) -> float:
    """Computes McNemar's test.

    Args:
      n1: the number of "wins" for the first condition.
      n2: the number of "wins" for the second condition.

    Returns:
      A p-value for McNemar's test.
    """
    n = n1 + n2
    x = min(n1, n2)
    dist = scipy.stats.binom(n, .5)
    return 2.0 * dist.cdf(x)


def mcnemar_midp(n1: int, n2: int) -> float:
    """Computes McNemar's test using the "mid-p" variant.

    This is based closely on:
    
    M. W. Fagerland, S. Lydersen, P. Laake. 2013. The McNemar test for 
    binary matched-pairs data: Mid-p and asymptotic are better than exact 
    conditional. BMC Medical Research Methodology 13: 91.

    Args:
      n1: the number of "wins" for the first condition.
      n2: the number of "wins" for the second condition.

    Returns:
      A p-value for the mid-p variant of McNemar's test.
    """
    x = min(n1, n2)
    return mcnemar_p(n1, n2) - dist.pmf(x)