1) Bell-shaped graphic 
(Learning Modules / Psychology / Measuring the unmeasurable) A graphical interpretation of a population that is 'bell shaped' as it has the highest frequency in the middle and this frequency diminishes the farther you get from the centre on either end. The mean, median, and mode are all equal in a perfect normal curve.
[n] - a symmetrical curve representing the normal distribution
bell-shaped curve noun a symmetrical curve representing the normal distribution
The symmetrical curve that represents the distribution of scores on many psychological attributes; allows researchers to make judgments of how unusual an observation or result is.
a bell-shaped curve showing a particular distribution of probability over the values of a random variable. Also calledCompare illus. under