Figure 15.3 Quality drift across many runs. Each dot is one run's score, and no single dot
is alarming—the slide is visible only in the population, as the band of runs sinks
gently to the right. The trend line, in accent, is the thing no single trace can show
you; it crosses the alert threshold near the right edge with no code change anywhere in
sight, which is why the countermeasure is a trend rule rather than a fixed cutoff.
