def _compute_std_dev(self, X):
        """Computes the standard deviation of a Gaussian Distribution with mean vector X[i]"""

        self._sigma = []
        if X.shape[0] <= 1:
            self._sigma = [0.0]
        else:
            for x_mean in range(X.shape[0]):
                std_dev = np.sqrt(sum([np.linalg.norm(x - x_mean) ** 2 for x in X]) / float(X.shape[0]-1))
                self._sigma.append(std_dev)

        return self._sigma