statsmodels.sandbox.descstats.sign_test(samp, mu0=0)[source]

Signs test.

  • samp (array-like) – 1d array. The sample for which you want to perform the signs test.
  • mu0 (float) – See Notes for the definition of the sign test. mu0 is 0 by default, but it is common to set it to the median.

Return type:

M, p-value


The signs test returns

M = (N(+) - N(-))/2

where N(+) is the number of values above mu0, N(-) is the number of values below. Values equal to mu0 are discarded.

The p-value for M is calculated using the binomial distrubution and can be intrepreted the same as for a t-test. The test-statistic is distributed Binom(min(N(+), N(-)), n_trials, .5) where n_trials equals N(+) + N(-).

See also