Answered above. 1 set 700X37 Top Contact Winter (non studded) at 35 psi, on flat bar road bike. No falls, but I don't ride this bike unless the weather and the pavement are pretty clear. Foul weather bike is a rigid MTB, running 26 x 1.9 Schwalbe Snow Studs at 30 psi. Fell twice last winter, both times on black ice at intersections when coming to a stop. Have also ridden Schwalbe Ice Spiker Pro 26 x 2.2 on a longtail cargo bike and that was like triding a tank.
My point is that studded tires do help a great deal but they can still slip on black ice. So can studded car tires. There is no such thing as a tire that will in and of itself prevent all slips and falls. People who buy studded tires expecting to be able to ride the same way they do on summer tires and clear pavement are not going to get the results they expect. Similarly, people with experience riding in winter who have not yet felt the need for studs, but are thinking about black ice specifically, probably aren't going to get the amount of improvement in grip that they might expect.
Seriously, 8 years riding every day, frequently as low as -30C. I am quite sure of what my tires, and I, can and cannot do.