Abstract
To finish in accordance with its originally planned duration or cost, a project that is not meeting its schedule or budget requires improved performance in the work that remains. This paper shows how to calculate the new productivity in terms of the average earned-value performance over the first part of a project, and it shows how the new productivity rate depends on the fraction of tasks completed. The completed task fraction beyond which recovery is impossible is calculated, and a point beyond which recovery is highly unlikely is suggested. Using an analytic approximation for an S-curve, these calculations are transformed into a temporal domain.
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Acknowledgements
I thank Homayoun Khamooshi for a careful reading and for catching an error in an earlier version, and an anonymous referee with helping place the material in a better context.
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Appendix A
Appendix A
Equations for the S-Curve solution
The normalized S-curve equation presented here, y(β) (where β is normalized time), asks the user to choose two parameters: 1) the slope of the rise in the middle part of the S-curve (r 0.67) and 2) the time at which approximately half the funds have been expended (β 1/2).12 The following set of expressions defines an S-curve in terms of these two values
where
and
As we desire, y=1 at the end of a project (y → y ∞>1 afterwards), and at β=β1/2, y=y ∞/2≈0.5. In the absence of any other information, choosing r 0.67=1 (two-thirds of the rise takes place in the middle third of the S) and β 1/2=0.5 yields the following explicit equation:
The above equation, used in the calculation in the main text, produces a typical S-curve. Increasing r 0.67 would sharpen the rise and flatten the curve at its two ends, but these changes would not change the nature of the results described above.
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Cioffi, D. Completing projects according to plans: an earned-value improvement index. J Oper Res Soc 57, 290–295 (2006). https://doi.org/10.1057/palgrave.jors.2602007
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DOI: https://doi.org/10.1057/palgrave.jors.2602007