Smaller change sets are reviewed faster and with fewer defects

Hypothesis

For a given team and codebase, change sets under a modest size threshold (for example 200 changed lines, excluding generated code) receive their first review comment sooner, are approved with fewer review rounds, and produce fewer defects found after merge than larger change sets.

Prediction

If the hypothesis holds, splitting a large change into a sequence of small, individually mergeable changes should reduce median time-to-approval and post-merge defects per changed line. If it does not hold, the sequence should show the same or worse figures because of coordination overhead.

Proposed test

1. Collect, for a defined period, the changed-line count, first-response time, number of review rounds and post-merge defects linked to each merged change.
2. Compare the groups above and below the threshold, controlling for author, component and change type.
3. Repeat after introducing an explicit size guideline to see whether the relationship survives the intervention.

Status

No test result is claimed here. Google's guide recommends small change lists for these reasons, which motivates the hypothesis; correlation in existing data would still not prove causation because harder changes tend to be larger.