Dear Upadhya,
A 'Bell Curve' is a statistical indicator of the distribution of Appraisal scores of employees in an organization. Ideally speaking, each Head of Department/ Function should have an access to this curve in respect of employees of their department/ function. The purpose is to normalize the scores at their own level. This normalization takes into account all the Managers who are lenient in rating their subordinates (means, a rating of 8 to 9 out of 10 is given to all) & the Managers who are too harsh/ conservative (meaning rating all employees in the range 4 to 6 points). Unless these rating tendencies are normalized, some good employees, placed under harsh managers, may be at a disadvantage compared to their counterparts reporting to lenient managers. Thus normalization helps in removing subjectivity & can be done easily if Bell Curves are readily available.
In some organizations, each Manager is given on-line access to the Bell Curve for his/ her own subordinates & is expected to rationalize the scores before forwarding the Appraisal reports to the next higher level of reporting. This enables normalization at the origin.
The final normalization takes place at the company level when appraisals of all employees are received by HR. A 'Bell Curve' for the complete organization is seen & its statistical mean and deviation are determined. These parameters are co-related to those at the Functional/ Departmental level and the aberrations are addressed through a consultative approach. This requires a high level of maturity of an organization's HR processes since the outcome is eventually used for grant of increments and/ or performance linked variable pay.
The entire process discussed above requires an automated HR environment. Effective tools such as 'EmpXtrack' are available in the market today to enable the 'Bell Curve' approach to performance evaluation becoming realistic.