def average_word_error_rate(word_error_rate_scores, combined_ref_len):
    """
    This function calculates average word error rate of the whole sentence.
    :param word_error_rate_scores: (float) Word error rate of each word.
    :param combined_ref_len: (int) Length of the reference sentence.
    :return: (float) Average word error rate.
    """
    return float(sum(word_error_rate_scores)) / float(combined_ref_len)