I have a 1-bit counter. It counts from 0 to 1, and then back to zero. It rests on a number for ten minutes. Every ten minutes in toggles.

I am holding this counter behind my back. What is the probability it displays a 1? You know it is either 0 or 1, and half the time it is 1. The probability is therefore 50%.

But suppose I show you the counter, and it displays a 0. The probability of it displaying a 1 is now 0%. Ten minutes later, the probability is 100%. The probability has become a function of time.

But the frequency—which is how much of the time the counter displays a 1—is still 50%. Probability and frequency are therefore not equivalent.