ITPEC FE Subject A April 2025 Question 42

Size in, effort and duration out — COCOMO estimates effort and schedule from the size of the software.

COCOMO (Constructive Cost Model) takes the estimated size in thousands of delivered source lines (KLOC) and applies empirical formulas, adjusted by cost drivers:

• •Effort in person-months: E = a × S^b, where S is the size in KLOC
• •Development time in months: T = c × E^d

So the chain is size → effort → duration, and dividing effort by duration gives the average team size.

Answer (a)

Why not others:

• •(b) — effort is not derived from duration; in COCOMO duration is itself computed from effort
• •(c) — reverses the model: size is the input, and effort is an output, never the starting point
• •(d) — also runs the chain backwards; duration is the last output, so neither size nor effort can be derived from it

Key rule: In size-based estimation models, size (KLOC or function points) is estimated first, then converted into effort, and schedule follows from effort.

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