68-95-99.7 rule

The 68-95-99.7 rule describes how data evenly spreads out around a average value in a bell-shaped (normal) distribution. It states that about 68% of data points are within one standard deviation (a measure of spread) from the mean, 95% are within two standard deviations, and 99.7% are within three. This helps us understand how typical or unusual a specific data point is: most fall close to the average, while extreme values are rare. The rule provides a quick way to estimate the likelihood of data points occurring within certain ranges in many real-world situations.