Existential fallacy
Belief that it is possible to reason about empty classes.
Sample size fallacy
Failure to consider sample size when estimating the probability of obtaining a particular value drawn from a known population.
Mathematical fallacy
Series of steps which is seemingly correct but contains a flawed argument, or a spurious proof of an obvious contradiction such as that 1 = 2. Fallacies differ from simple mistakes in that there is an element of concealment in the presentation of the proof.