Appeal to probability is a logical fallacy where someone assumes that because something is possible or even probable, it is therefore certain to happen. This reasoning disregards the actual likelihood of the event. It treats a degree of possibility as a guarantee. The fallacy occurs when this assumption of certainty based on probability influences a conclusion.
For example, someone might say, "There's a 20% chance of rain tomorrow, so it will definitely rain." In this example, the speaker assumes that because there is a probability of rain, it is a certainty. The 20% chance indicates a possibility, but it does not guarantee rain; it also suggests an 80% chance of no rain.