What do you mean by empirical estimation models? Explain COCOMO model with suitable example?

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Stands for Constructivie Cost Model

As with all estimation models, it requires sizing information and accepts it in three forms: object points, function points, and lines of source code.

Application composition model - Used during the early stages of software engineering when the

following are important

– Prototyping of user interfaces

– Consideration of software and system interaction

– Assessment of performance

– Evaluation of technology maturity

Early design stage model – Used once requirements have been stabilized and basic software architecture has been established

Post-architecture stage model – Used during the construction of the software

Organic, Semidetached and Embedded software projects

Organic: A development project can be considered of organic type, if the project deals with developing a
well understood application program, the size of the development team is reasonably small, and the

team members are experienced in developing similar types of projects.

Semidetached: A development project can be considered of semidetached type, if the development
consists of a mixture of experienced and inexperienced staff. Team members may have limited

experience on related systems but may be unfamiliar with some aspects of the system being developed.

Embedded: A development project is considered to be of embedded type, if the software being developed is strongly coupled to complex hardware, or if the stringent regulations on the operational
procedures exist.

The basic COCOMO model gives an approximate estimate of the project parameters. The basic COCOMO

estimation model is given by following expressions:

Effort = a1 x (KLOC)a2 PM (person Month)

Time of Development = b1 x (Effort) b2 Months

Where, a1,a2,b1,b2 are constants for each category of software products

Estimation of Effort

Organic: Effort = 2.4 (KLOC) 1.05 PM

Semi-detached: Effort = 3.0 (KLOC) 1.12 PM

Embedded: Effort = 3.6 (KLOC) 1.20 PM

Estimation Time of Development

Organic: Time of Development = 2.5 (Effort) 0.38 Months

Semi-detached: Time of Development = 2.5 (Effort) 0.35 Months

Embedded:Time of Development = 2.5 (Effort) 0.32 Months

Example:

Assume that the size of an organic s/w product has been estimated to be 32,000 lines of source code. Assume that the average salary of software be Rs. 15,000/- month. Determine the effort required to develop the software product and the nominal development time.

Effort= 2.4 x (32) 1.05 = 91 PM

Time of development = 2.5 x (91) 0.38 = 14 months

Cost= 14 x 15,000 = Rs. 2,10,000/-