cost12 1 Question of the Day u How important is it to be able to estimate the cost of a software project?

cost12 2 Questions u PLQ 11

cost12 3 Cost Estimation An estimate of the effort and duration, associated costs of equipment, travel and training and the rationale for the calculations

cost12 4 Recommendation u If you are involved with cost estimation, I recommend the following book u Tom DeMarco, Controlling Software Projects, Yourdon Press, NY c1982

cost12 5 Definition of Estimate (DeMarco) u Default: – "An estimate is the most optimistic prediction that has a non-zero probability of coming true" u Proposed: – "An estimate is a prediction that is equally likely to be above or below the actual result"

cost12 6 Estimates should not become goals u DeMarco argues that the estimation and the management decision about pricing or goals should be separate.

cost12 7 Estimate

cost12 8 Cost Estimate u should not be a contract bid u should not be a schedule u should be input into the management decision to determine the above u should be re-estimated frequently

cost12 9 TTYP1 u Given the following data, what would be your estimate for a project that would be about 200K? What would you use for a cost estimation formula? u Historical data –project 1 100K50 prog-months –project 220K10 prog-months –project 314K7 prog-months –project 416K8 prog-months

cost12 10 Confidence in your estimate u How confidence are you in this estimate? u Would you stake your job/grade on this estimate? u What would be your concerns? u What could you do to increase your confidence? u What would you consider to be a successful estimate?

cost12 11 Problems u Programmer variability u Product complexity u Variability of goal u Conflict of goals u Lack of detailed product description u Variation in effort to reuse code u Emergence of new processes, methods and tools

cost12 12 Cost Estimation Models u LOC models – Boehm's COCOMO – Price S – Putnam's Model (SLIM) u non-LOC models – Function Points u combination – COCOMO2

cost12 13 Prediction Formulas E=  X    >1  <1  =1 TTYP2 – which one did Henry Ford experience? Which one happens in your project? Size cost A non-zero gamma would shift line up or down

cost12 14 Tuesday, 10/17 Read Pressman pp SOS section PLQ – Monday, 10am