## Elementary Statistics: A Step-by-Step Approach with Formula Card 9th Edition

mean=215.0 standard deviation=20.8 All the data are within 2 standard deviations. Chebyshev’s theorem:predicts that at least $75\%$ of the data fall within 2 standard deviations. It seems Chebyshev’s theorem did not work well for this case.
mean=215.0 standard deviation=20.8 within 2 standard deviations of the mean: 173.4 to 256.6 contains all the data points, Chebyshev’s theorem: for $k=2$, $1-1/2^2=0.75$, at least $75\%$ of the data fall within 2 standard deviations. It seems Chebyshev’s theorem did not work well for this case.