# stats - Statistics#

## gammapy.stats Package#

Statistics.

### Functions#

 `cash`(n_on, mu_on[, truncation_value]) Cash statistic, for Poisson data. `cash_sum_cython`(counts, npred) Summed cash fit statistics. `cstat`(n_on, mu_on[, truncation_value]) C statistic, for Poisson data. `f_cash_root_cython`(x, counts, background, model) Function to find root of. `get_wstat_gof_terms`(n_on, n_off) Goodness of fit terms for WSTAT. `get_wstat_mu_bkg`(n_on, n_off, alpha, mu_sig) Background estimate `mu_bkg` for WSTAT. `norm_bounds_cython`(counts, background, model) Compute bounds for the root of `_f_cash_root_cython`. `wstat`(n_on, n_off, alpha, mu_sig[, mu_bkg, ...]) W statistic, for Poisson data with Poisson background. `compute_fvar`(flux, flux_err[, axis]) Calculate the fractional excess variance. `compute_fpp`(flux, flux_err[, axis]) Calculate the point-to-point excess variance. `compute_flux_doubling`(flux, flux_err, coords) Compute the minimum characteristic flux doubling and halving over a certain coordinate axis for a series of measurements. `compute_chisq`(flux) Calculate the chi-square test for `LightCurve`.

### Classes#

 `CashCountsStatistic`(n_on, mu_bkg) Class to compute statistics for Poisson distributed variable with known background. `WStatCountsStatistic`(n_on, n_off, alpha[, ...]) Class to compute statistics for Poisson distributed variable with unknown background.