Statistical software quality assurance in software engineering involves ______.

Explanation

Statistical SQA means collecting defect data, classifying every defect by its underlying cause, and then applying the Pareto principle to isolate the vital few causes that produce most of the defects and fix those first. That is option (3). Option (4) is the near-miss distractor: it wrongly says every problem found should be corrected, which discards the whole point of separating the vital few from the trivial many. Sampling instead of exhaustive testing (1) is a general testing tactic, and customer opinion surveys (2) measure perceived quality, not defect causes.