Figure 2.6: Figure 4.5 Not All Bell-Shaped Curves Are Normal Distributions In bell-shaped curves, the midpoint is the mean, median, and mode, and frequencies decrease symmetrically as values move away from the midpoint. Though all the curves shown here are bell-shaped, not all bell-shaped curves are normal distributions. The normal distribution is a specific bell-shaped curve, defined by the percentage of cases that fall within specified regions. Only the last curve is a normal distribution.