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Bell Curve | Meaning and Definition

What is a bell curve?

The Bell Curve is a mathematical representation of normal distribution. It is so named because its shape resembles a bell. The curve is symmetrical, with the tallest point in the middle and two tails that taper off at either side. Half of the data points will fall below the average (the mean), and half will fall above it. 

Most of the data points will be clustered around the middle, with fewer data points as you move away from the center. This distribution curve is typical for many real-world phenomena, from IQ scores to height to test scores. Because it’s so common, statisticians have developed ways to work with data that follows a pattern. 

Bell curve system in performance management

The appraisal is a popular performance management tool used by organizations to assess and manage employee performance. The system relies on a statistical bell-curve distribution to group employees into three categories: above average, average, and below average. 

Organizations that use this performance appraisal typically conduct annual or biannual performance reviews, during which managers rate each employee’s performance on a scale from one to five, with three being average. This rating is then compared to the rest of the employees in the organization, with those who fall at the top and bottom of the bell curve considered above or below-average performers, respectively. 

There are some potential disadvantages to using this system, however. For example, it can create feelings of competition and resentment among employees.

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