filter the poor performing curve
        
        Returns
        -------
        None

def filter_curve(self):
        """filter the poor performing curve
        
        Returns
        -------
        None
        """
        avg = np.sum(self.trial_history) / self.point_num
        standard = avg * avg * self.point_num
        predict_data = []
        tmp_model = []
        for i in range(NUM_OF_FUNCTIONS):
            var = 0
            model = curve_combination_models[i]
            for j in range(1, self.point_num + 1):
                y = self.predict_y(model, j)
                var += (y - self.trial_history[j - 1]) * (y - self.trial_history[j - 1])
            if var < standard:
                predict_data.append(y)
                tmp_model.append(curve_combination_models[i])
        median = np.median(predict_data)
        std = np.std(predict_data)
        for model in tmp_model:
            y = self.predict_y(model, self.target_pos)
            epsilon = self.point_num / 10 * std
            if y < median + epsilon and y > median - epsilon:
                self.effective_model.append(model)
        self.effective_model_num = len(self.effective_model)
        logger.info('List of effective model: ', self.effective_model)