On your TI-83 or TI-84 Press CLEAR Press STAT Press 1 Enter the 12 numbers in L1 Press STAT Press the right arrow key to highlight CALC Press 1 Press ENTER _ Read the mean as x = 34.33333333 Read the standard deviation as Sx=7.784989442 Chebyshev's theorem states thatof the data will lie within standard deviations of the mean, where . Using k=1.1, and the mean and standard deviation above, Chebyshev's theorem tells us that AT LEAST 17.3% of the data lies between 25.77 and 42.897. In fact 83.3% of it does! Using k=1.5, and the mean and standard deviation above, Chebyshev's theorem tells us that AT LEAST 55.5% of the data lies between 22.66 and 46.01. In fact 83.3% of it does! Using k=2, and the mean and standard deviation above, Chebyshev's theorem tells us that AT LEAST 75% of the data lies between 18.76 and 49.90. In fact 100% of it does! ----------------------------- The empirical rule says that if a histogram of the data is approximately bell-shaped, like this: then 1. approximately 68% of the data will fall between 1 standard deviation below the mean and 1 standard deviation above the mean. That is, if the given data is approximately bell-shaped, then 68% of the data should fall between 34.33333333 - 7.784989442 or 26.54834389 and 34.33333333 - 7.784989442 or 42.11832278 Actually 10 of the 12 data values fall between these, so that's % Also 2. approximately 95% of the data will fall between 2 standard deviations below the mean and 2 standard deviations above the mean. That is, if the given data is approximately bell-shaped, then about 95% of the data should fall between 34.33333333 - 2(7.784989442) or 18.76335445 and 34.33333333 + 2(7.784989442) or 49.90331222 Actually all 12 of data values fall between these, so that's %. Edwin