4.3 A team has decided to make a robust design study on a simple cap of the type used for PET bottles. The team wants to avoid a situation where the consumers find it unpleasant to open, so openability is the issue. The team has noted that they can observe or control a number of things in the test, but would like some help in classifying them as signal, response, noise, or control. These things are:

 speed of opening, rad/s;

 total energy;

 peak force or torque;

 storage time;
 height of grooves;
 radial force from finger to cap;
 roundness of grooves;
 cap diameter;
 cap height;
 cap wet or dry;
 bridges between tampering band and cap, 4 or 8 (same total area);
 contact area, finger–cap;
 cap wall stiffness;
 force (torque) as a function of time (or vice versa);
 force (torque) as a function of angle (or vice versa).