I've made the mistake of engaging the #NoEstimates crowd in questions about the usefulness of their idea. Not a group that likes to get questions, by the way. They use the old Ron Jeffries approach (which has since passed for him) of *well just try it to see if it works for you. *

The big question is:

If you been asked to make a decision about something related to software development, say a make buy decision, is making an estimate of the comparative costs or comparative durations a good idea?

Turns out that is not a question that can be asked in that crowd. So I learned my lesson again. In the mean time, this diversion caused me to dig out my slightly tattered edition of *Time Series Analysis: Forecasting and Control*, Box and Jenkins, 1976. I'm working on a presentation for the Fall Integrated Program Management Conference for the use of time series analysis to forecast the Estimate At Completion using the CPI/SPI numbers at the Control Account Level available in the XML submissions of the Contract Performance Report.

The approach currently used to forecast the EAC wouldn't get a D in any statistical analysis class.

- Take all the past performance an accumulate it to a single number
- Take the current period as a single number
- Forecast the future performance of this number is a
*linear*ratio - Do not adjust this number for the underlying variances of the past
- Do not adjust this number of the assured underlying variances of the future
- Commit millions and many times billions of dollars on the forecast

Along with the Box book I use, there are of several books for applying R to time series analysis. Here's the list of resources for those interested in this topic.

*Time Series Analysis: Forecasting and Control*; George E. P. Box and Gwilym M. Jenkins, Holden-Day, 1978*Empirical Model-Building and Response Surfaces*, George E. P. Box and Norman P. Draper, John Wiley, 1987.*Bayesian Inference in Statistical Analysis*, George E. P. Box and George C. Tiao, Wiley Interscience, 1992.*Introduction to Multiple Time Series Analysis*, Helmut Lutkepohl, Springer, 2005.*Time Series Analysis and Its Applications with Examples in R*, Robert H. Shumway and David S. Stoffer, Springer, 2011.

So when you're asked *how much will this cost* or *when will you be done spending my money for the things I asked you to develop* or *what's the confidence you'll be ready for the "go live" date or better yet the "launch" date of this project*, hopefully youranswer woun't be *well you see we don't make estimates on our project work, we just develop small increments of fucntionality till the time and money runs out*.

**Yea Right**