Takes a group of equal length lists and averages them across each index.

        Returns
        -------
        mean_layers: [float]
            List of values averaged by index
        overall_mean: float
            Mean of the averaged values.

def calc_average_parameters(parameter_layers):
        """Takes a group of equal length lists and averages them across each index.

        Returns
        -------
        mean_layers: [float]
            List of values averaged by index
        overall_mean: float
            Mean of the averaged values.
        """
        mean_layers = [numpy.mean(x) if x[0] else 0 for x in parameter_layers]
        overall_mean = numpy.mean([x for x in mean_layers if x])
        return mean_layers, overall_mean