Bell Curve - On What Basis The % Are Being Decided?

Can anyone explain to me how the bell curve works? On what basis are the percentages decided?

Hi, in short, the bell curve works based on the sample data selected by the analyst or researcher. You can find many definitions on an internet search. If you could let me know where you would like to introduce it, that would be helpful. Looking forward to your response.

Please click on the links in the sidebar on the right; you will find answers to your questions.

Well,

We are using the Bell Curve in our organization for annual appraisals. The following criteria are ideal for a construction company:

Criteria: Appraisers and Reviewers will review the performance as per the defined Rating scale:

Rating Levels

Competency

A Excellent: Exceeds the requirements of competencies and shows competencies at the next level.

B Very Good: Demonstrates all competencies at the expected level and exceeds some.

C Good: Demonstrates all competencies at the expected level.

D Satisfactory: Demonstrates some competencies at the expected level and needs improvement in some.

E Poor: Needs to improve all competencies; does not demonstrate competencies at the required level for the roles.

Bell Curve: Please note that the overall ratings should be distributed among all eligible employees as per the "Bell Curve Ratings."

The details of the Bell Curve Concept are attached for your reference, and it will help you in the distribution of performance ratings at your vertical level.

Example: If we have 100 employees eligible for the PMS, the HOD will ensure that 70% of employees are in the Good Category, 10% in Very Good, 5% in Excellent Category, 10% in Satisfactory, and not more than in Poor.

Hi,

The Bell Curve is generally used for performance distribution within an organization or a unit. This concept is primarily utilized in the performance appraisal process. Typically, not all employees in an organization can achieve the same performance level. Therefore, after assessing the organization's performance, financials, etc., for a particular period/year, management determines that a certain percentage of employees should fall into categories such as high flyers, good performers, average performers, or poor performers. This distribution curve should align with the actual health of the organization, avoiding excessive skewing towards either the right or left side.

Regards,
Manoj

Dear Raisa,

To reinforce your learning, it would be better if you could summarize the concept of the bell curve as you have understood and post it here. In case there is any mistake, experts will correct it.

As per my understanding, the appraiser segregates people based on their ratings in a bell curve shape. For example, (Assume a 1-5 Rating Scale) if there are 500 employees in an organization, then out of those 500, 10% will have a rating of 1, i.e., Very Good, 20% will have a rating of 2, i.e., Good, 40% will have a rating of 3, i.e., Average, 20% for rating 4, i.e., Poor, and 10% for rating 5, i.e., Very Poor. So basically, an appraiser is segregating those 500 employees according to their ratings under one bell curve.

Sir, are bell curves formed department-wise or is there one bell curve for the entire organization?

Dear Raisa,

Please read the article by Ron Ashkenas at [Forbes](http://www.forbes.com/sites/ronashkenas/2012/09/05/why-performance-assessment-curves-often-bend-the-wrong-way/) to understand why performance assessment curves often bend the wrong way. Also, please note the remarks at the bottom to learn how to cite one's own work to avoid self-plagiarism.

Please also read Rosh Ashkenas on HBR.org, where people have commented on the application of the Bell Curve.

Appraisals, being ratings, cannot produce bell-shaped curves due to their distributions. Anyone with frequency distributions on notional scales may very well be found here. These distributions are not bell-shaped.