Trims data based on propensity score using the cutoff
		selection algorithm suggested by [1]_.
		
		This method should only be executed after the propensity score
		has been estimated.

		References
		----------
		.. [1] Crump, R., Hotz, V., Imbens, G., & Mitnik, O. (2009).
			Dealing with Limited Overlap in Estimation of
			Average Treatment Effects. Biometrika, 96, 187-199.

def trim_s(self):

		"""
		Trims data based on propensity score using the cutoff
		selection algorithm suggested by [1]_.
		
		This method should only be executed after the propensity score
		has been estimated.

		References
		----------
		.. [1] Crump, R., Hotz, V., Imbens, G., & Mitnik, O. (2009).
			Dealing with Limited Overlap in Estimation of
			Average Treatment Effects. Biometrika, 96, 187-199.
		"""

		pscore = self.raw_data['pscore']
		g = 1.0/(pscore*(1-pscore))  # 1 over Bernoulli variance

		self.cutoff = select_cutoff(g)
		self.trim()