Here is a quote from a training manual at work regarding SLIM and software estimation:
Notice also, there is a correlation between Effort and Defects. This means, the more people there are assigned to a project of a given size, the more Defects there will be.
Effort is person-time (person-years, person-months) for the project. Defects is the count of defects detected at any point in the lifecycle. Size is defined as the use cases, function points, or SLOC that compose the project.
This seems counterintuitive, assuming a good process and capable engineers. For example, having more people means more eyes on all of the artifacts (requirements specs, designs, code, tests). Aside from having more eyes, my intuition suggests that there is little relationship between effort and defects on a project that utilizes appropriate quality techniques.
I haven't been able to find any documents, aside from those about the Putnam Model (which is used by SLIM), that suggest any kind of known relationship between defects and effort or defects and number of people on a project. Is this a known relationship, and is the assertion that "more people = more defects" valid?