Allen Chou says to YSITD >>> (1 / np.sqrt(2 * np.pi * sigma_d)) * np.exp( (-(100 - mu_d) ** 2) / (2 * np.square(sigma_d)) ) 0.0795707027249985 >>> stats.norm.cdf(x=100, loc=mu_d, scale=sigma_d) 0.818348929556551