The Impact of People on Cost and Effort


Just how much can people factors influence your project cost and effort?  24.6 percent!  In other words, the least experienced team (the bottom 15 percent) can require up to 24.6 times as much effort to complete a project as the most experienced team (top 10 percent.) In Professional Software Development: Shorter Schedules, Higher Quality Products, More Successful Projects, Enhanced Careers, Steve McConnell writes about the Cocomo II model and how personnel factors influence project cost and effort.

The Cocomo II Model
How much do personnel factors influence the project’s cost and effort over the base estimate?  The Cocomo II Estimation model uses 7 factors to figure out the influence score.  The influence score is used to adjust a base effort estimate.

7 Personnel-Oriented Factors
According to McConnell, these are the 7 personnel-oriented factors and their influence rating:

  • Application Experience (1.51)
  • Communications Factors (1.53)
  • Language and Tool Experience (1.43)
  • Personnel Continuity (1.51)
  • Platform Experience (1.40)
  • Programmer Capability (1.76)
  • Analyst Capability (2.00)

The 7 personnel-oriented factors can exert a cummulative influence range of 24.6.  (Multiply each factor … 1.51 x 1.53 x 1.43 … etc.)

3 Seniority-Oriented Factors
Experience alone is a big factor.  According to McConnell, here’s the three seniority-oriented factors and their influence rating:

  • Application Experience (1.51)
  • Language and Tool Experience (1.43)
  • Platform Experience (1.40)

The 3 seniority-oriented factors can exert a cumulative influence range of 3.02.

Key Take Aways
I think this gem supports what I already intuitively know and have experienced but helps quantify it.  Here’s my key take aways:

  • Experience plays an enormous role in cost and effort.
  • No matter how good your process is, it won’t make up for good people.
  • Nonprocess-oriented organizations succeed if they have the right people.

Additional Resources