def get_mean_and_stddevs(self, sites, rup, dists, imt, stddev_types):
        """
        See :meth:`superclass method
        <.base.GroundShakingIntensityModel.get_mean_and_stddevs>`
        for spec of input and result values.
        """
        # extract dictionaries of coefficients specific to required
        # intensity measure type and for PGA
        C = self.COEFFS[imt]
        C_PGA = self.COEFFS[PGA()]

        # compute median pga on rock (vs30=1100), needed for site response
        # term calculation
        # For spectral accelerations at periods between 0.0 and 0.25 s, Sa (T)
        # cannot be less than PGA on soil, therefore if the IMT is in this
        # period range it is necessary to calculate PGA on soil
        if imt.name == 'SA' and imt.period > 0.0 and imt.period < 0.25:
            get_pga_site = True
        else:
            get_pga_site = False
        pga1100, pga_site = self._compute_imt1100(C_PGA,
                                                  sites,
                                                  rup,
                                                  dists,
                                                  get_pga_site)

        # Get the median ground motion
        mean = (self._compute_magnitude_term(C, rup.mag) +
                self._compute_distance_term(C, rup, dists) +
                self._compute_style_of_faulting_term(C, rup) +
                self._compute_hanging_wall_term(C, rup, dists) +
                self._compute_shallow_site_response(C, sites, pga1100) +
                self._compute_basin_response_term(C, sites.z2pt5))

        # If it is necessary to ensure that Sa(T) >= PGA (see previous comment)
        if get_pga_site:
            idx = mean < np.log(pga_site)
            mean[idx] = np.log(pga_site[idx])

        stddevs = self._get_stddevs(C,
                                    sites,
                                    pga1100,
                                    C_PGA['s_lny'],
                                    stddev_types)
        return mean, stddevs
See :meth:`superclass method
        <.base.GroundShakingIntensityModel.get_mean_and_stddevs>`
        for spec of input and result values.