def std_dev(list_of_nums):
    """
    Returns standard deviation values for a list of numbers
    :param list_of_nums: a list of numbers
    :return: standard deviation val
    """
    length = len(list_of_nums)
    mean = sum(list_of_nums)/length

    std_dev = (sum([(num - mean)**2 for num in list_of_nums])/length)**0.5
    return std_dev