import math


def SE_calc(item1, item2):
    """
    Calculate standard error with binomial distribution.

    :param item1: parameter
    :type  item1: float
    :param item2: number of observations
    :type item2: int
    :return: standard error as float
    """
    try:
        return math.sqrt(
            (item1 * (1 - item1)) / item2)
    except Exception:
        return "None"