def _effect_level(effect_size, method='cohend'):
    """
    Determines magnitude of effect size.
    """
    if not isinstance(method, str):
        raise TypeError('method must be of type str')
    if method not in ['cohend', 'cliffdelta']:
        raise ValueError(
            "method must be one of the following strings: 'cohend', 'cliffdelta'"
            )
    effect_size = abs(effect_size)
    if method == 'cliffdelta':
        if effect_size < 0.147:
            return 'negligible'
        elif effect_size < 0.33:
            return 'small'
        elif effect_size < 0.474:
            return 'medium'
        else:
            return 'large'
    if method == 'cohend':
        if effect_size < 0.2:
            return 'negligible'
        elif effect_size < 0.5:
            return 'small'
        elif effect_size < 0.8:
            return 'medium'
        else:
            return 'large'
