Implement the cumulative standard normal Φ(z) with math.erf and reproduce the four table lookups from the lesson to four decimals.

Answer

import math def Phi(z): """Cumulative standard normal: P(Z <= z), the z-table's cell.""" return 0.5 * (1 + math.erf(z / math.sqrt(2))) print(f"Phi(1.28)={Phi(1.28):.4f}") print(f"Phi(-2.05)={Phi(-2.05):.4f}") print(f"P(Z>0.67)={1 - Phi(0.67):.4f}") print(f"P(-1.5<Z<0.75)={Phi(0.75) - Phi(-1.5):.4f}")

IBS1 §6.2 for the problem types and App. A11 for the contrast (CC BY 4.0 — no lookup transplanted); cumulative convention per the S21 W7 handout (shape only)