Hi Liz,
I am glad you are almost through with your project.
Bell Curve is a percentage wise calculation.
Hence the post you read where in its 10% (Superior Performers), 70% (Average Performers) and 20% (Non Performers). Wherein the 70% can be considered the assets and the 20% Liabilities.
Now for calculation of the Bell Curve you will need the Average(mean), Standard deviation of the original data and you will need the lower limit and the upper limit.
To fill in the formulaes and the values please refer the word document attached previously by me, its a help by microsoft to create a bell curve and instead of creating random numbers use the data that you already have. Insert the formulaes mentioned as in the document and you will have your bell curve since in the formulae we have opted for three deviations and hence its sure to form a bell curve.
(Please note individual values has to be inserted so as to determine where the personnel is placed). The chart is more for demonstration purpose and to see how well the company has improved keeping in reference to your first bell curve, you can determine individual performances by the data itself.
Regards,
AJ