def D_est(Ht_est, Hs_est, n):
    """Basic Equation: ((Ht-Hs)/(1.0-Hs))*(n/(n-1))"""
    n = float(n)
    if (1.0 - Hs_est) * (n / (n - 1)) == 0.0:
        return 0.0
    else:
        D_est = (Ht_est - Hs_est) / (1.0 - Hs_est) * (n / (n - 1))
        return D_est
