For
our purposes, examples are number of CMMI process area goals attained, percent
of defects found per month, number of trained people on a project team, and percent
of projects using function points to calculate size. Variable data are data that
vary and must be measured on a continuous scale. These measurements are usually
quantitative measures. Examples are length, time, volume, height, effort expended,
memory utilization, and cost of rework.
Control charts help detect and differentiate between noise (normal variation of
the process) and signals (exceptional variation that warrants further investigation).
An everyday example of noise in a process is the ???white lab-coat effect.??? This effect
is what happens when you go to the doctor to get your blood pressure checked.
Anyone who has a tendency to high-blood pressure will generally become a little
nervous during this procedure. Therefore, the blood pressure reading taken by the
medical professional (in the white lab coat) has been known to skew higher than
if the reading had been taken in the comfortable surroundings of your own home.
Pages:
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529