code: def get_b_star(x_star, y_err, y_mean, y_segment):
      
      #print "x_star, should be same as Xcorr / NRM"
      #print x_star
      x_star_mean = numpy.mean(x_star)
      x_err = x_star - x_star_mean
      b_star = -1* numpy.sqrt( old_div(sum(numpy.array(y_err)**2), sum(numpy.array(x_err)**2)) )  # averaged slope
      #print "y_segment", y_segment
      b_star = numpy.sign(sum(x_err * y_err)) * numpy.std(y_segment, ddof=1) / numpy.std(x_star, ddof=1)
      #print "b_star (should be same as corr_slope)"
      #print b_star
      return b_star
docs: input: x_star, y_err, y_mean, y_segment
      output: b_star (corrected slope for delta_pal statistic)