Exactly. There are no absolutes here. All you can do is take an educated guess, with no guarentees.
Precisely correct. As you go through your daily life you make educated guesses about all manner of things. Including whether or not someone deserves a little closer look or may be a higher safety risk.
My goal was to find out if anyone had specific criteria that would set off their alarms. If I'm in my local mom & pop grocery store and the guy ahead of me is fidgety, I do a quick check. Are his actions because he's in a hurry and the person at the counter is slow? Are his actions due to maybe needing the restroom? Any conspicious bulges around the waist? Pockets? However, my alarms will be jangling if he has tattoos on the back of his neck or all over his arms.
Profiling? Stereotyping? Sure. Experience says that criminals tend to dress a certain way. Few muggings are committed by perpetrators wearing a Hart Shaffner and Marx suit. And I'd guess it is fairly rare for a liquor store to be robbed by a man in a tuxedo. This doesn't mean every young male wearing baggy clothes is going to be a criminal or a gangbanger. But given a choice between watching a pair of 22 year olds, one wearing slacks, dress shoes and a polo shirt and one wearing baggy clothing and a hoodie... yeah, Mr. Wannabe bad-boy gets more looks. If only because the baggies might better conceal a weapon.