Box Basic Cocomo Effort Formulas for Three Modes

1 05

Effort for Organic Mode: E = 2.4x (Size) Effort for Semidetached Mode: E = 3.0 x (Size]'12 Effort for Embedded Mode: E = 3.6 x (Size)'20

Table 11-2. Basic COCOMO Effort and Development Time Formulas




Effort Formula Effort = a x (Size)b

Development Time Formula




E = 2.4 x (S)1 05

TDEV = 2.5 x(E?'38 Months




1 12 E = 3.0 x (S)

TDEV = 2.5 x(E?'35 Months




1 20 E = 3.6 x (S)

TDEV = 2.5 x(E?'32 Months

The same-size project yields different amounts of effort when it is considered to be of different modes: Suppose that a project was estimated to be 200 KLOC. Putting that data into the formula Effort = a x (Size)b

Effort for the organic mode would be estimated at 2.4 x (200) = 2.4(260.66) = 626 staff-months.

Effort for the semidetached mode would be estimated at 3.0 x (200)1 12 = 3.0(377.71) = 1,133 staff-months. Effort for the embedded mode would be estimated at 3.6 x (200)1 20 = 3.6(577) = 2,077 staff-months.

After effort is estimated, an exponential formula is also used to calculate a project duration, or completion time (time to develop, TDEV). Project duration is expressed in months.

Basic COCOMO Project Duration Estimation

Boehm devised three formulas (see Box 11?3) to be used for development time in the same fashion as he did with effort.

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