Calculate confidence interval.

    :param mean: mean of data
    :type mean : float
    :param SE: standard error of data
    :type SE : float
    :param CV: critical value
    :type CV:float
    :return: confidence interval as tuple

def CI_calc(mean, SE, CV=1.96):
    """
    Calculate confidence interval.

    :param mean: mean of data
    :type mean : float
    :param SE: standard error of data
    :type SE : float
    :param CV: critical value
    :type CV:float
    :return: confidence interval as tuple
    """
    try:
        CI_down = mean - CV * SE
        CI_up = mean + CV * SE
        return (CI_down, CI_up)
    except Exception:
        return ("None", "None")