A rule that states that when a distribution is bell-shaped (normal), approximately68% of the data values will fall within 1 standard deviation of the mean; approximately 95% of the data values will fall within 2 standard deviations of the mean; and approximately 99.7% of the data values wi...
It is bell-shaped and the fatness of the bell depends on its standard deviation. Examples are given in Figure 21.20 and 21.21. Sign in to download full-size image Figure 21.20. A normal distribution with µ = 0 and σ = 1 (called the standard normal distribution N(0,1)). Sign in ...