Chebyshev and Empirical Rule Worksheet Mean: Standard deviation: k: Interval: Chebyshev lower bound, 1 - 1/k^2: Observed proportion: Is the distribution approximately normal-shaped? If yes, compare with 68%, 95%, or 99.7%. If no, explain why the Empirical Rule is not justified. Original educational material created for STATLAB Academy. Do not reproduce third-party textbook content.