def get_chisquare(ci):
    """
    Upper-tail critical values of chi-square distribution
    with 2 degrees of freedom
    """
    if ci == 0.90:
        return 4.605
    elif ci == 0.95:
        return 5.991
    elif ci == 0.975:
        return 7.378
    else:
        return 5.991