Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!bionet!agate!ucbvax!mtxinu!sybase!edward From: edward@vangogh.sybase.com (Ed Hirgelt) Newsgroups: comp.software-eng Subject: Re: Using COCOMO to estimate development schedules Message-ID: Date: 6 Apr 89 20:49:31 GMT References: <351@tahoma.UUCP> <4148@ttidca.TTI.COM> <7518@thorin.cs.unc.edu> <4183@ttidca.TTI.COM> Sender: news@sybase.sybase.com Organization: Sybase, Inc. Lines: 35 In-reply-to: hollombe@ttidca.TTI.COM's message of 3 Apr 89 19:56:28 GMT In article <4183@ttidca.TTI.COM> hollombe@ttidca.TTI.COM (The Polymath) writes: + Apparently I didn't make myself clear. My (former) boss didn't compare + COCOMO figures to seat-of-the-pants estimates. He plugged actual figures + from real, completed projects into the COCOMO formulas and compared the + COCOMO projections with the actual project figures. + He found the COCOMO projections to be wrong by as much as 50%. But isn't this a necessary part of using the model -- tuning it to the characteristics of the software and environment that you are trying to represent. Since this is a model and since there are things in it to tweak (if I remember what little I've read about COCOMO), you can take your actual results, evaluate the model and see what it estimates. From that determine changes to the model that make it more accurate. With a reasonable base of data (it sounds like your boss had that) it should be possible to get a much better fit for a particular environment. Then the model becomes a better predictor. Models only work well when their assumptions are met. If your environment, project, or staff don't match the model, the model needs to be enhanced. I have often wished that I had the records necessary to tune a model and make it moderatey accurate. I know -- I should start keeping them. One of these days I will, really I will. Ed -- --------------------------------------------------- Ed Hirgelt sun!sybase!edward Sybase, Inc. edward@sybase.com 6475 Christie Ave Emeryville, Ca. 94608