bell curve

n. The graphical representation of a normal distribution which appears as a unimodal (single-peak), symmetrical curve that resembles a bell. In a bell curve, the majority of scores are in the middle of the distribution and fewer scores near the ends of the distribution (however, the tails of the distribution are infinite and the base of the bell is never complete); this pattern is responsible for producing the familiar bell shape. While the area under a bell curve is always constant (equal to 1), the height and spread of the curve vary as a mathematical function of the mean and standard deviation. The mean provides the midpoint for the peak of the curve and the standard deviation tells how tightly the data is clustered around the mean. When the standard deviation is small, the bell-shaped curve is steep; when the standard deviation is large, the bell curve is relatively flat. The x-axis of the bell curve is the horizontal dimension; the x-axis pertains to the value in question. The y-axis is the vertical dimension and accounts for the number of data points for each value on the x-axis.

- bjm