Three weeks after planting, the heights of tomato plants have a mean of 29.4 cm and a standard deviation of 2.1 cm. Chebyshev inequality was used to show that there is at least a 75% chance that a tomato plant has a height within two standard deviations of the mean, that is, within the interval [25.2, 33.6
However, if the tomato plant height are taken to be normally distributed, then this probability can be calculated much more precisely. In fact, the probability is about 95%. Moreover, there is a probability of about 99.7% that a tomato plant has a height within three standard deviation of the mean, that is, the interval [23.1, 35.7].